The mother of a baby found Tuesday in a garbage bin possibly didn't realize she was pregnant, police say. (Dave Gilson/CBC)

A man who jumped into a Calgary dumpster to rescue a newborn that had been discovered by another passerby says he later found out the baby boy was his son, he told CBC News on Wednesday.

The infant was found on Tuesday at about 1:20 p.m. MT in a garbage bag in a trash bin at a townhouse complex at Fourth Street and 40th Avenue N.W.

Police said Wednesday that the mother likely didn't know she was pregnant and could face criminal charges related to her actions following the birth.

The man who claims to be the father of the baby said he was unaware his girlfriend was even pregnant.

"I pulled into my parking spot and hadn't even got to the back of my truck and a girl said, 'I think hear a baby in the dumpster.' So I, you know — no knowledge at this time that this is my kid whatsoever — I went running over," he said.

"And I jumped in and I removed the stuff and I personally opened the bag. My first sight of my baby was covered in garbage."

The man, 30, said his girlfriend had complained Tuesday morning she was not feeling well.

'My first sight of my baby was covered in garbage.'— Man who says he pulled his baby out of a dumpster

"When I looked at her, she didn't seem to be in distress," he said. "So I thought nothing of it, and I proceeded to go to work.

"But just around one o'clock I got a bad feeling in my gut, and I was like, 'I'm going to go home for lunch,'" he said.

The man and the woman who first heard the infant called 911, while another passerby used his shirt to keep the child warm.

The baby was taken to hospital and is in stable condition in the neonatal intensive-care unit at Foothills hospital.

Mother didn't know she was pregnant: police

One hour after the baby was found, a woman was taken to hospital in stable condition by emergency medical services. Police confirmed Wednesday she's the mother.

Investigators believe she was not aware of her pregnancy until the birth, and that the father was not aware he had a son until after the incident, said Staff Sgt. Leah Barber, who is with the Calgary police child abuse unit.

The man said detectives informed him at about 9:30 p.m. Tuesday that the baby's mother was his girlfriend.

"And from that point on my world has been going 10,000 places," he said.

The mother was to undergo a psychological exam Wednesday.

Depending on its outcome, she could be charged with attempted murder, failing to provide the necessities of life or child abandonment, police said.

"We still have to consult with the Crown," Barber said. "Obviously there's more to the story as far as the woman is concerned."

"It was within hours of birth, which is incredibly lucky that the passerby responded to the cries," said Barber.