Police: Marathon security tight, despite no known threats

BOSTON — About 5,000 uniformed and undercover police officers, drones, bomb-sniffing dogs and trucks blocking some streets are just some of the security measures being used to protect runners and spectators at the Boston Marathon.

Federal and state law enforcement officials said Tuesday that there is no known credible threat to this year's marathon on April 16, which comes five years after two bombs planted near the finish line killed three spectators and wounded more than 260 others.

Authorities say they have learned from recent mass casualty events and terrorist attacks, including the Las Vegas shooting and attacks in Europe carried out by people driving vehicles.

Boston police will deploy officers on rooftops near the marathon route, which goes through eight cities and towns.

Associated Press