Tests have revealed the baby boy found at the recycling plant in Scunthorpe was a newborn, but further tests are needed to determine the cause of death.
The body was discovered at Bell Waste Control in Scunthorpe, North Lincolnshire, on 2 May. The baby was found by a member of staff as he was sorting material for recycling.
Humberside Police said a post-mortem examination has confirmed the infant was a newborn boy but a cause of death has yet to be established.
A teenage girl has come forward claiming she is the mother, following a plea from the police.
She was been taken to Scunthorpe General Hospital, where she was admitted for postnatal care.
Police are continuing their inquiries into the circumstances of the baby's death.
A statement from Humberside Police said: "A post-mortem examination of the baby found at Bell Waste Control in Scunthorpe on Wednesday, 2 May has confirmed that it was a newborn baby boy.
"However, the cause of death is yet to be established as the results came back inconclusive and further tests will now be carried out. The teenage mother remains in hospital receiving medical care and police inquiries into the circumstances of what happened are continuing."