Firefighters in Kentucky's largest city were working to rescue a person trapped under rubble Thursday at a construction site near the citys 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, Louisville Fire Chief Brian ONeill said. The worker is about 10 to 12 feet (3 to 3.7 meters) below ground, ONeill said.Rescuers continued to work to free the worker Thursday evening as night fell. Officials had a crane and ladders going into the hole, which is several feet wide.There were five 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.ONeill said firefighters were on the scene within three minutes and began conducting a trench rescue. Workers will try to clear debris from around the mans arms and chest so he can be given medical aid, the chief said.The rescue could take hours, ONeill 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.