The 25-year-old was in a stable condition in The Alfred hospital this morning after his bizarre 11-hour ordeal ended when paramedics and firefighters pulled him, covered in grease and fat, from a duct that ventilates the complex’s restaurants.

A Victoria Police spokeswoman said South Melbourne detectives had taken over the investigation but were yet to speak to the man. No charges had been laid, she said.

The slippery character had climbed into a duct about 11pm on Wednesday and crawled deep into the building before coming to a sticky stop in, Metropolitan Fire Brigade Commander Wayne Garrard said.

Staff at Automatic restaurant at Crown arrived at work at 10am yesterday to hear noises and cries for help from the duct above their pizza oven, and called emergency services.

A paramedic in disposable overalls with a safety harness and rope attached was sent into the duct to check the man’s condition, before firefighters extracted him, more than 11 hours after he started his strange journey.

‘‘It looked like a cow had just given birth,’’ Commander Garrard said, describing the state of the extracted intruder.

‘‘He was covered in brown grease and fat. I guess because it was so slippery he couldn’t go anywhere.

''He’s a very, very lucky boy, I tell you. Where he ended up he was right on top of the pizza oven. It’s lucky that he regained consciousness and yelled out.’’

Commander Garrard said it appeared the man had illegally gained access to the duct from a stairwell near the roof, and crawled about 30 metres before he got into trouble in his metre-by-half metre prison.

Despite the ordeal, the man claimed he could not remember how he got inside.

‘‘I think he might have been under the influence of something. Whether it was a bit of a prank or something, I’m not sure,’’ Commander Garrard said.

‘‘When he came out he was conscious and breathing. He couldn’t remember how he got in there but he could give us give his name and address and that sort of thing.’’