The decomposing remains of 11 infants were found on Friday after Michigan authorities received an anonymous tip that sent them to a shuttered funeral home in eastern Detroit.

The bodies were found in a box and a coffin that were hidden in a drop ceiling between the first and second floors of the Cantrell Funeral Home, Lt. Brian Bowser of the Detroit Police Department told reporters on Friday night. It was unclear how long the remains had been there.

He said the Michigan Department of Licensing and Regulatory Affairs received a letter about the remains on Friday afternoon and went to the funeral home. Agency officials then called the police.

Lieutenant Bowser said officers discovered “11 remains of infants, stillborns.”

The state department shut down the funeral home in April because of “deplorable, unsanitary conditions and other violations,” it said in a statement at the time.