MONTREAL -- Black Friday shopping turned into chaos at the Galeries d'Anjou in east-end Montreal tonight after what police called an "irritating gas" was used during a fight, sending one person to hospital.

People ran for the exit before being officially evacuated, said an employee at the mall -- it was unclear at first what was happening, and rumours spread that someone had a weapon.

"We were all scared because we didn't even know what was going on," said Megan Raimondo, 18, who was at her job at the Winners in the mall when the incident began, just before 7 p.m.

"The Winners is right next to the mall exit, so we could see people running to get out," she said.

"Outside it was really chaotic -- there were a lot of cars, a lot of the exits were blocked, people were trying to figure out how to get out of the mall."

Police said at about 7:45 p.m. that two groups "got into an altercation" inside the shopping mall.

It appeared that one of the people involved in the fight released some kind of noxious gas similar to tear gas, said Montreal police spokesman Raphael Bergeron.

Bergeron said he doesn't yet know exactly what the substance was or how much of it was released. While no serious injuries were reported, he said later Friday evening that one person went to hospital to be treated for their exposure to the gas, while others suffered minor discomfort.

Shoppers had to be sent outside because the noxious gas was spreading through the entire mall, he said.

Police arrived, along with firefighters who needed to "clean out the air," Bergeron said. He said there are no suspects yet, but police are reviewing security footage.

Mall management said there was no weapon other than the gas and even reports of a major fight were overblown.

"It was more like a pepper-spray prank" that sent people running from the centre of the mall, where it happened, to escape the effects, Galeries d'Anjou general manager Sebastien Perron told CTV News.

BUSIEST DAY AT THE MALL IN MONTHS

Raimondo said that with Black Friday sales, "it was pretty packed today" at Galeries d'Anjou, within the confines of distancing rules.

Her store, for example, has a capacity of 150 people and it was at capacity, she said, with shoppers lining up (with distance) in the mall hallways to get into various stores. The mall was supposed to close at 9 p.m. tonight.

Before police or mall security were in touch to explain what had happened, shoppers were warning others that someone may have a weapon in the mall, Raimondo said -- the first she heard of it was from two separate shoppers in the store.

Staff elsewhere in the mall, at different spots and with different vantage points, later compared notes. One account that Raimondo heard from a friend at another store was that a canister of pepper spray had dropped during a fight, maybe even by accident, she said.

That other employee said that "two people were fighting and they dropped a bottle of pepper spray, and it sounded like a gun when it dropped, so that's what caused everyone to freak out," she said.

She said she hadn't felt any effects of the gas and didn't know anyone else who reported feeling the effects.

Perron said the mall will reopen at the usual time on Saturday morning.