A baby whose body parts were found in a sewage treatment works was recently born prematurely, police said today.
Humberside Police said the baby was born no later than 24 weeks into its mother's pregnancy and appealed for her to seek medical advice.
The body parts were found at the sewage works at Saltend, near Hull, on Wednesday afternoon.
A force spokeswoman said a post-mortem examination had revealed the age of the baby and medical tests were ongoing.
She said: "A post mortem shows the baby was aged no more than 24-weeks gestation and is likely to have been very recently born."
Police said they were "concerned" about the welfare of the mother.
Detective Superintendent Chris Kelk said: "We would urge the mother of the baby to visit her doctor or local hospital to seek medical attention.
"She does not have to come and speak to the police but we would like to know that she is OK."
Contractors discovered the body parts while clearing a tank at the sewage works on Hedon Road.
Officers cordoned off the scene to allow scenes of crime officers to investigate at the sprawling treatment plant just outside Hull.
Anyone with information is asked to contact Humberside Police on 0845 6060222 or the major incident room on 01377 228789.