U.S. Capitol Police evacuated several floors of the Dirksen Senate Office Building on Tuesday after receiving a bomb threat. Police later said they found nothing suspicious. (Reuters)

Updated 1:33 p.m.

U.S. Capitol Police say they found nothing suspicious after they evacuated a large part of the Dirksen Senate Office Building due to a bomb threat.

Capitol Police said in statements that they evacuated part of the building because of a phone call reporting a suspicious package in room SD-340. They described the call as a bomb threat.

They found nothing hazardous in that room, their latest statement said. In the Russell Courtyard, they found a suspicious package, but it turned out to be a lunch cooler.

When Capitol police officers flooded in just after noon to scour the building, their attention appeared to focus on the third floor room where the Homeland Security Committee was about to wrap up a hearing on the Transportation Security Administration.

Committee Chairman Ron Johnson (R-Wis.) interrupted a witness and ordered the room emptied after an aide whispered in his ear.

As people departed, police rushed in to inspect the room. The north side of the building was entirely evacuated.

The committee had just completed a robust discussion about the cost of adding more bomb-sniffing dogs to enhance airport security. They heard that the dogs cost about $100,000 to train and about $60,000 per year after that.

Minutes later, bomb-sniffing canines were working their way through the now-vacant committee room and adjacent rooms and corridors.