LEVITTOWN - Police are investigating the death of an infant at a Levittown day care center this afternoon. Day care owner Karen Schriver told police that she found the 4-month-old boy cold and unresponsive more than an hour after putting him down for a nap. Police say she was taking care of at least nine children at the time, and there was another adult on the premises. The center is licensed with New York State, but has previously gotten in trouble for hiring an assistant not cleared by the state to care for children. Police say there are no signs of criminal activity, but are awaiting autopsy results to determine the cause of death.