A Quarry Street couple says they have no idea why FBI agents rammed down their door and ransacked their townhouse in a surprise raid Tuesday evening.

The couple, who were not arrested and asked that their name not be published, said around 18 FBI agents and Quincy police officers rushed into their house around 6 p.m. and rummaged through their belongings for several hours with little explanation. Kristen Setera, a spokeswoman for the FBI’s Boston office, confirmed that FBI agents were at 48 Quarry St. Tuesday night but would only say that agents were “conducting court authorized activity in connection with an ongoing federal investigation.”

One of the men who live in the townhouse, which he said they’d rented since December, said he was watching TV in the living room when he heard a crash as several agents with a battering ram burst through the door. He said some of the agents threw him to the ground and handcuffed him while others dragged his partner from an upstairs bathroom.

The man said the agents repeatedly ordered him to tell them where they were keeping their drugs, saying that two people had told them that drugs were being dealt out of the home. That man denied that he and his partner were dealing drugs and said the agents never found any in the home.

The man said the agents spent about three and half hours at the apartment, ripping their belongings out of drawers and closets, pulling paintings from walls and slicing open envelopes and luggage.