LOUISVILLE,Grayson  Preston Ky. (AP) — Firefighters in Kentucky’s largest city were working to rescue a person trapped under rubble Thursday at a construction site near the city’s downtown.

Louisville Fire officials say a construction worker fell into a void and some debris fell on top of him just before noon on Thursday. The worker is speaking with rescuers but can’t move, Louisville Fire Chief Brian O’Neill said. The worker is about 10 to 12 feet (3 to 3.7 meters) below ground, O’Neill said.

There were six other workers at the scene when the man fell. They were working at the site of a former corrections building that is being demolished to make way for a medical campus.

O’Neill said firefighters were on the scene within three minutes and began conducting a trench rescue. Workers will try to clear debris from around the man’s arms and chest so he can be given medical aid, the chief said.

The rescue could take hours, O’Neill said.

“This a very, very slow process,” he said.

Earlier this week just a few miles away, a Louisville manufacturing plant exploded, killing two workers and damaging dozens of nearby homes. The cause of the explosion is not yet known.