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Jacqueline Benson shoots the starting piston for the elite womens' start of the 117th running of the Boston Marathon, in Hopkinton, Mass., Monday, April 15, 2013. (AP Photo/Stew Milne) ( Boston Marathon )

Participants start in the elite men's division of the 117th running of the Boston Marathon in Hopkinton, Massachusetts April 15, 2013. REUTERS/Dominick Reuter ( ATHLETICS-MARATHON/BOSTON )

Participants start in the elite women's division of the 117th running of the Boston Marathon in Hopkinton, Massachusetts April 15, 2013. REUTERS/Dominick Reuter ( ATHLETICS-MARATHON/BOSTON )

Elite mens marathoners including Levy Matebo, fourth from left, and Markos Geneti, front right, run in the 117th Boston Marathon in Wellesley, Mass., Monday, April 15, 2013. (AP Photo/Michael Dwyer) ( Boston Marathon )

Elite female marathoners, front row from left, Rita Jeptoo, Mamitu Daska, Meserat Debele, Tirifi Beyene, Alemitu Begna, Shalane Flanagan, Ana Felix and Sabrina Mockenhaupt compete on the course in Wellesley, Mass., Monday, April 15, 2013. (AP Photo/Michael Dwyer) ( Boston Marathon )

A motorcycle camera crew photographs the lead men's finishers as they pass the 26th mile marker, which was dedicated to the victims of the Sandy Hook Elementary School shooting in Newtown, Conn., during the 2013 running of the Boston Marathon in Boston, Monday, April 15, 2013. (AP Photo/Charles Krupa) ( Boston Marathon )

Lelisa Desisa Benti of Ethiopia (front) runs a few seconds ahead of Micah Kogo of Kenya and Gebregziabher "Gebre" Gebremariam of Ethiopa as they sprint to the finish of the men's division of the 117th Boston Marathon in Boston, Massachusetts April 15, 2013. REUTERS/Neal Hamberg ( ATHLETIC-MARATHON/BOSTON )

Lelisa Desisa Benti of Ethiopia crosses the finish line to win the men's division of the 117th Boston Marathon in Boston, Massachusetts April 15, 2013. REUTERS/Neal Hamberg ( ATHLETIC-MARATHON/BOSTON )

Lelisa Desisa Benti of Ethiopia crosses the finish line to win the men's division of the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. (Photo by Jim Rogash/Getty Images) ( 166662432 )

Gebregziabher Gebremariam of Ethiopia is helped after he stumbled over the finish line to finish second in the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. (Photo by Jim Rogash/Getty Images) ( 166663568 )

Men's division winner Lelisa Desisa Benti of Ethiopia poses for a photo after winning the men's division of the 117th Boston Marathon in Boston, Massachusetts April 15, 2013. REUTERS/Jessica Rinaldi ( ATHLETICS-MARATHON/BOSTON )

Shalane Flanagan approaches the finish line to finish fourth in the women's division of the 2013 Boston Marathon in Boston Monday, April 15, 2013. (AP Photo/Elise Amendola) ( Boston Marathon )

Yolanda Caballero runs alone at the twelve-mile mark on the Boston Marathon course in Wellesley, Mass., Monday, April 15, 2013. (AP Photo/Michael Dwyer) ( Boston Marathon )

Rita Jeptoo of Kenya crosses the finish line to win the women's division of the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. (Photo by Jim Rogash/Getty Images) ( 166662284 )

Rita Jeptoo of Kenya crosses the finish line to win the women's division of the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. (Photo by Jim Rogash/Getty Images) ( 166662160 )

Rita Jeptoo of Kenya kisses the pavement after she crossed the finish line to win the women's division of the 2013 Boston Marathon in Boston Monday, April 15, 2013. (AP Photo/Elise Amendola) ( Boston Marathon )

Rita Jeptoo of Kenya sits wrapped in a towel as she rests in the finish area after winning the women's division of the 2013 Boston Marathon in Boston Monday, April 15, 2013. (AP Photo/Elise Amendola) ( Boston Marathon )

Shalane Flanagan, right, is embraced by Kara Goucher, both of the United States, after finishing the 2013 running of the Boston Marathon in Boston, Monday, April 15, 2013. Flanagan finished fourth and Goucher sixth in the women's division of the race. (AP Photo/Charles Krupa) ( Boston Marathon )

Lelisa Desisa Benti (L) of Ethiopia reacts after winning the men’s division of the 117th Boston Marathon as Duval Patrick, governor of Massachusetts watches on April 15, 2013 in Boston, Massachusetts. (Photo by Jim Rogash/Getty Images) ( 166662954 )

Rita Jeptoo of Kenya is presented with the laurel wreath by Massachusetts Governor Deval Patrick after winning the women's division of the 117th Boston Marathon in Boston, Massachusetts April 15, 2013. REUTERS/Neal Hamberg ( ATHLETIC-MARATHON/BOSTON )

The 117th Boston Marathon women's division winner Rita Jeptoo of Kenya reacts as she is handed the Boston Marathon trophy in Boston, Massachusetts April 15, 2013. REUTERS/Jessica Rinaldi ( ATHLETICS-MARATHON/BOSTON )

The 117th Boston Marathon Men's division winner Lelisa Desisa Benti, of Ethiopia, (L) and women's division winner Rita Jeptoo of Kenya pose for a portrait with the trophy in Boston, Massachusetts April 15, 2013. REUTERS/Jessica Rinaldi ( ATHLETICS-MARATHON/BOSTON )

The first wave of runners starts the 117th running of the Boston Marathon in Hopkinton, Massachusetts April 15, 2013. REUTERS/Dominick Reuter ( ATHLETICS-MARATHON/BOSTON )

Chris Royer, from Coventry, Vt., raises his hands as he starts of the 117th running of the Boston Marathon, in Hopkinton, Mass., Monday, April 15, 2013. (AP Photo/Stew Milne) ( Boston Marathon )

Supporters cheer on participants in the 117th running of the Boston Marathon in Wellesley, Massachusetts April 15, 2013. REUTERS/Dominick Reuter ( ATHLETICS-MARATHON/BOSTON )

Runners start the 117th running of the Boston Marathon, in Hopkinton, Mass., Monday, April 15, 2013. (AP Photo/Stew Milne) ( Boston Marathon )

Supporters cheer on participants in the 117th running of the Boston Marathon in Wellesley, Massachusetts April 15, 2013. REUTERS/Dominick Reuter ( ATHLETICS-MARATHON/BOSTON )

Spectators watch runners pass by at the start of the 117th running of the Boston Marathon, in Hopkinton, Mass., Monday, April 15, 2013. (AP Photo/Stew Milne) ( Boston Marathon )

A runner douses himself with water during the 117th running of the Boston Marathon in Wellesley, Massachusetts April 15, 2013. REUTERS/Dominick Reuter ( ATHLETICS-MARATHON/BOSTON )

A runner steps over discarded cups near a water station in the 117th running of the Boston Marathon in Wellesley, Massachusetts April 15, 2013. REUTERS/Dominick Reuter ( ATHLETICS-MARATHON/BOSTON )

Defending champion Josh Cassidy, of Canada, adjusts his wheelchair prior to the wheelchair division start of the 117th running of the Boston Marathon, in Hopkinton, Mass., Monday, April 15, 2013. (AP Photo/Stew Milne) ( Boston Marathon )

Defending champion Joshua Cassidy, of Canada, fifth front right, starts the wheelchair division of the 117th running of the Boston Marathon, in Hopkinton, Mass., Monday, April 15, 2013. (AP Photo/Stew Milne) ( Boston Marathon )

Dick Hoyt, foreground left, pushes his son Rick on the Boston Marathon course in Wellesley, Mass., Monday, April 15, 2013. (AP Photo/Michael Dwyer) ( Boston Marathon )

Hiroyuki Yamamoto of Japan crosses the finish line to win the men's wheelchair division of the 117th Boston Marathon in Boston, Massachusetts April 15, 2013. REUTERS/Jessica Rinaldi ( ATHLETICS-MARATHON/BOSTON )

Tatyana McFadden of the United States reacts as she crosses the finish line to win the women's wheelchair division of the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. (Photo by Jim Rogash/Getty Images) ( 166664867 )

Hiroyuki Yamamoto of Japan reacts after winning the men's wheelchair division of the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. (Photo by Jim Rogash/Getty Images) ( 166664027 )

Tatyana McFadden of the U.S. smiles as she poses for a portrait with the Boston Marathon trophy after winning the women's wheelchair division of the 117th Boston Marathon in Boston, Massachusetts April 15, 2013. REUTERS/Jessica Rinaldi ( ATHLETICS-MARATHON/BOSTON )

Hiroyuki Yamamoto of Japan reacts during ceremonies after winning the men's wheelchair division of the 2013 Boston Marathon in Boston Monday, April 15, 2013. (AP Photo/Elise Amendola) ( Boston Marathon )