More than a dozen people at charity hockey event were hospitalized in Ottawa on Saturday after showing symptoms of carbon monoxide poisoning.

The participants were taking part in a Movember fundraising tournament at the Complete Hockey Development Centre in west Ottawa on Saturday, when some of the hockey players fell ill.

According to the rink’s website, the three-on-three event was scheduled to take place between 3 and 9 p.m.

Fire crews arrived at the hockey centre around 1 a.m. after players had been taken to hospital, but were unable to detect carbon monoxide in the building.

Though air quality tests turned up negative, an Ottawa Fire spokesperson confirmed to CTV Ottawa’s Claudia Cautillo that blood test results showed several of the players had high levels of carbon monoxide in their system.

The manager of the complex later blamed a faulty exhaust vent for the incident, which has since been repaired. The manager said the facility was operating like normal Sunday.

One of the players, Chris Monteith, was at home recovering Sunday. He went to Queensway Carleton Hospital Saturday, where he was told he had high levels of carbon monoxide poisoning.

“I think all of us are a little short of breath,” Monteith said. “It’s definitely an unfortunate thing, we all feel quite sick still.”

Though most of the players were released after being treated, some were still feeling the effects a day later.

“My cousin that was at the hospital there with me until 8 a.m. last night getting treated, he actually had to go back because he was coughing up blood and throwing up blood this morning.”

The players, who spent more than eight hours at the rink Saturday, said the symptoms crept up on them.

“At first I just thought maybe we were all tired. We’d been at the rink all day playing a lot of game,” said Bradley Clifford, another player. “Then the minute I heard it could have been carbon monoxide poisoning, I was pretty worried.”