A 31-year-old man has been arrested on suspicion of attempted murder after a newborn baby boy was dumped in hospital toilets.
The infant had to be resuscitated after he was found by security staff in the A&E department of the Royal Albert Infirmary in Wigan just after midnight on Wednesday.
Detective Inspector Martin Reddington from Greater Manchester Police said: "This is an awful situation, I am just so happy I am able to say that the baby boy is doing well.
"We have made an arrest and we will be thoroughly investigating how this happened."
The hospital's Accident and Emergency was closed overnight but has since reopened, Greater Manchester Police said.
Officers are appealing for anyone who was in the department on Tuesday evening and saw a man and a woman in and around the toilets to come forward.
Mr Reddington added: "We are appealing for anyone who may have been in the A&E department between 7pm and midnight and perhaps saw a man and a woman in and around the toilets or saw anything unusual to get in touch with police as soon as possible.
"I would like to take this opportunity to praise the staff at the Royal Albert Infirmary, without doubt their heroic actions saved the life of this newborn baby."
Andrew Foster, chief executive of Wrightington, Wigan and Leigh NHS Foundation Trust, praised the worker who found the baby.
He said: "I would like to thank all staff who were involved for their professionalism and calmness during the incident, particularly the diligent member of staff who discovered the baby and raised the alarm. I'm very proud of the way our staff worked, their quick response without doubt saved the baby's life."
Anyone with any information can call police on 0161 856 7124 or Crimestoppers anonymously on 0800 555 111.