Newsday says the U.S. Occupational Safety and Health Administration, which looks into work-related accidents, is investigating.
It says the storm drain in Uniondale, Long Island, is on private property owned by Manhattan-based real estate company Philips International. Police say a company worker had placed the plywood on the hole. Philips didn't return a request for comment.
Joe Hranicka spent more than seven hours inside the drywell. He was cleaning a parking lot Monday night when he stopped to move the plywood and fell in, landing on dry debris and a chair. Police say the drain's metal cover was found in the hole.