The Special Investigations Unit has been called in after police officers shot and wounded two men following a collision in the heart of Toronto's financial district.

SIU spokesperson Rose Bliss says it's still not clear what triggered a red car to smash into an unmarked police cruiser at the intersection of Bay and King Streets at about 2:30 a.m.

The plainclothes officers exited their damage vehicle and approached the suspects. After confronting the driver and passenger, the detectives shot and wounded both men, Bliss said.

Details of the altercation are still being investigated. A police source, however, told CTV News officers opened fire after the car drove at them.

One victim, identified as a 20-year-old man, was shot in the head. The other victim was shot in the chest and abdomen, Bliss said.

Both are at St. Michael's Hospital in stable condition.

The intersection where the shooting occurred was closed to traffic for more than eight hours. Streetcar service was re-routed and special TTC buses were brought in.

Toronto police are not commenting on the incident, citing a department policy not to speak about a situation once the SIU has been called in.

The incident was captured on security video and the footage will be reviewed.

The SIU investigates all incidents involving police and civilians that result in serious injuries, death or allegations of sexual assault.

With a report from CTV's Chris Eby