TORONTO - Emergency workers faced a scene right out of a horror movie Tuesday after a group of actors dressed as zombies fell off a platform during a film shoot in Toronto.

At least 16 actors on the set of "Resident Evil: Retribution" were injured in the accident just before 8 a.m. at a studio in the city's west end, police said. Officials said none of the injuries was life-threatening.

At first, emergency responders were thrown by the bizarre sight of the background actors made up to look like zombies, and it was more difficult for crews to assess their injuries, said Toronto EMS spokesman Peter Macintyre.

"I can imagine walking in, you know you're the first paramedic on the scene and you've got a whole lot of patients and you take one look and they look like zombies," said Macintyre.

"That's quite frankly not something you see every day," he said.

"It did kind of catch us off guard when we walked in," added Toronto Police Sgt. Andrew Gibson.

The actors fell about a metre and a half as the cameras rolled at the Cinespace Film Studios, where the fifth instalment of the franchise based on the popular video game series is shooting.

One actor suffered a cracked rib while another had a leg stress fracture and another suffered a possible back injury, the film's producers said.

Seven of the actors had already returned to the set by Tuesday afternoon, Davis Films/Impact Pictures (RE5) Inc., Constantin Film International GmbH said in a release.

Star Milla Jovovich was not on the set when the incident happened and wasn't injured, a studio spokeswoman said.

"It appears that there were a group of actors on a platform, that one platform had wheels and they were moving over to another platform," said Const. Tony Vella.

"As soon they were moving over, the wheels moved, causing them to fall," he said.

The film's producers said the platform "separated from the set, creating a gap that several performers fell through."

The Ontario Ministry of Labour is investigating the incident.

"They are sending an inspector and an engineer," said ministry spokesman William Lin, adding that about 50 workers were on the platform when it moved.