Even for people used to being around drug addicts, it was scary.

"I've never seen anything like it,” says Robert Daly. “I have never seen people drop like flies like that. I have never seen multiple possible O.D.'s to that effect."

Daly is talking about what happened Wednesday night on George Street in Ottawa’s Byward Market. Five people quickly became ill within minutes of each other after ingesting crack cocaine . Eye witnesses say they exhibited overdose-like symptoms.

Two of them were described as being in critical condition, including the man James Johnson ran to help. "He was like blue in the face. His lips were blue,” says Johnson. “I could identify that he was obviously having an overdose from an opiate."

"Literally five minutes later, the next guy was on the ground, dropped,” he adds. “He wasn't even breathing, nothing."

Police and paramedics were quickly on the scene. "When we found those two critical patients they had only about 4 or 5 minutes to go and certainly they would have been dead," says J.P. Trottier of the Ottawa Paramedic Service.

There are reports of a few others becoming ill in the same area, but apparently not related to the same drug.

Police have arrested a 29-year-old male on drug-related charges. They have not yet identified him but say he is known to police.

Remarkably, the victims are expected to make a full recovery.

Samples of the drug have been sent to Health Canada for analysis. The initial suspicion is that the crack was laced with morphine. Drug dealers have been known to do this to make it more potent and more addictive.

The police, health officials and the local shelters are trying to warn users of the added danger. Workers at the nearby Salvation Army Ottawa Booth Centre have stepped up their rounds to keep an eye on people. "We do on a very regular basis. But we tripled, quadrupled our walking around inside and outside the building," says Executive Director Marc Provost.

Meanwhile the mood on the street is one of alarm, fear, and even anger. They know using crack is dangerous at the best of times. But this, they say, is cruelly targeting people at their most vulnerable, people for whom “don’t do drugs” is not so easy an option.

"People are going to come down here and sell their crack. That's what they do. That’s what this place is,” says Carter Preston. “But someone to do that, it could have been any one of us, you know?"