Rodgers Rop led a Kenyan sweep of the first four spots in the Boston Marathon on Monday, winning in 2 hours, 9 minutes, 2 seconds.

Margaret Okayo, also of Kenya, won the women's race in 2:20:43, taking 62 seconds off the course record. She pulled away from two-time defending champion and world record-holder Catherine Ndereba in the final mile.

Kenyans had won Boston 10 consecutive years before Lee Bong-ju of South Korea ended the streak last year. Lee was the top non-Kenyan again, but he was fifth after falling out of the lead pack by the 19-mile mark.

South Africa's Ernst Van Dyk won the wheelchair race by almost three minutes in 1:23:19. Edith Hunkeler of Switzerland won the women's wheelchair race in 1:45:57.

Nearly 17,000 runners crossed the red, white and blue starting line under tight security and joined by 600 police officers.

There were no specific threats directed at the marathon, but race organizers followed the trend of other big sporting events by beefing up security.

The police officers who ran supplemented an unprecedented force of 1,500 guarding the race. Although they had no official duties, the running police were prepared to leave the course if needed.

Also on hand were 415 National Guard troops and another 1,500 law enforcement officers from other agencies, including the FBI. Helicopters, bomb-sniffing dogs, hazardous materials teams and radiation detectors were added or increased this year, and the whole crew was in contact with the state's emergency bunker in Framingham. Runners submitted information for background checks.

Runners were serenaded by national songs at the start of the annual Patriots Day race, and at the finish, four 45-by-90-foot U.S. flags were unfurled.