Authorities are crediting an on-site medic at Occupy Vancouver for saving the life of a man who overdosed at the camp Thursday morning.

The man, who appears to be in his late 20s or early 30s, went into cardiac arrest at around 9:15 a.m. behind the Vancouver Art Gallery, where dozens of protesters have been living in tents since mid-October.

Vancouver Fire Chief John McKearney said the quick response of a medic at the camp, who revived the man's breathing and pulse before ambulance paramedics arrived, likely prevented a tragic outcome.

"CPR needs to be initiated within four or five minutes. This is what certainly saved this person's life," McKearney said.

It is unclear what drug the man overdosed on.

McKearney said firefighters have been at the protest site since it began on Oct. 15, and Thursday's incident is the first of its kind.

Protester Jay Peachy insisted that the Occupy community does not support the use of drugs or alcohol on the site, but said Thursday's incident reflects an unfortunate reality in the city.

"This is what happens in the everyday community in Vancouver in the Downtown Eastside," Peachy said. "This is the real world, and the more we ignore it and put our blinders to it, the more this happens."

Witnesses have reported smelling marijuana smoke at the protest site, but Thursday's incident is the first confirmed report of hard drug use.

Jamileh Hargraves, who is advocating for a more family-friendly atmosphere at the camp, says the presence of addicts has hurt the movement.

"Of course we want to support people who are struggling in their lives, the homeless population," said Hargraves. "However, because we are catering to those individuals, it has diminished a lot of the community values that we would like to see in this area."

Drug use at the Occupy Vancouver camp says nothing about the protest or its goals, Hargraves argued.

Mayor Gregor Robertson said the overdose has him worried.

"I have huge concerns with safety on the site," he told reporters.

"The situation is degenerating and the city is monitoring this very closely."

He says city staff are negotiating with protesters daily in an attempt to convince them to move on, but he isn't prepared to set a hard deadline.