Police investigate the scene of the accident. (CBC)

Toronto police are trying to figure out how a taxi crushed a cyclist's leg early Friday morning.

The damaged leg was later amputated.

The incident happened at around 2:30 a.m. at the corner of Dovercourt Road and Argyle Street.

Witnesses told police they heard shouting, followed by the sound of a crash. Then they saw a Beck's taxi leaving the scene and a cyclist lying at the side of the road in obvious pain.

A few hours later, a taxi driver contacted police and said he had been assaulted just before the incident. Officers are questioning the driver, but he's not under arrest.

"We're trying to determine the sequence of events and how this escalated from the sound of voices to what we have right now, a male in hospital with fairly significant injuries fighting for his life," said Const. Tim Burrows.

The 36-year-old cyclist needed emergency surgery, and his leg had to be removed.

Burrows said the cyclist had been crushed between the taxi and a utility pole.

There was "extensive severe trauma to one of his legs and a fractured pelvis," he said. "We haven't had an opportunity to speak with him. We're just waiting for the hospital for an update as to the severity."