Law Enforcement Searches Boston Apartment

RYM MOMTAZ, CARLOS BOETTCHER and RHONDA SCHWARTZ report:

An unidentified Boston Marathon runner leaves the course crying near Copley Square following an explosion in Boston on April 15, 2013. (Winslow Townson/AP Photo)

Teams of federal and local law enforcement agents searched an apparently vacant fifth floor apartment on Ocean Avenue in the Boston suburb of Revere just hours after a pair of bombings killed at least three people at the Boston Marathon, residents told ABC News.

Marcus Worthington, a law student who lives in the apartment complex, told ABC News he saw dozens of law enforcement vehicles arrive at his building Monday afternoon, including FBI, ATF and local police and fire departments. Other neighbors who declined to be named said FBI agents entered the complex around 7:30 p.m. and went to the fifth floor.

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Though law enforcement agencies have not confirmed the action was related to Monday's bombing, Worthington told ABC News an agent from the ATF told him they were responding to a tip "concerning the incident at the Boston Marathon."

"The agent said they were searching an apartment for a dangerous device," Worthington said. But the agent added there was no longer "anything to worry about."

Residents said the apartment building is home to many students and security is generally relaxed.

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