Two women are in police custody and a third is in hospital in grave condition after a nightclub fight spilled into the Granville Street strip overnight.

A vicious fight broke out between two women inside the Caprice nightclub around 2 a.m. on Thursday but quickly ended up on the sidewalk outside.

People who watched the violence said one of the women collapsed on the ground and was unconscious as another woman punched and kicked her.

"She should not have thrown those punches. She was already unconscious – she wasn't going to do anything," said witness Theoron Nesbitt.

Another witness, Garrison Johnson, said he knelt by the woman's side but was told by a bouncer to leave her alone.

He estimated the woman was knocked out for five minutes after being kicked in the temple.

"The girl was already unconscious on the ground, and then the attacker came around her and started hitting her in the face," he told CTV News.

The 28-year-old woman was rushed to hospital, where she is in "grave condition," police said.

Two suspects in the attack fled the scene on foot, before emergency crews arrived.

About half an hour later, two women were taken into custody as they exited a cab near Hastings and Abbott streets. Police said they believe the women were involved in the attack.

Investigators continue to interview witnesses, and are reviewing video captured both inside and outside of the club. Anyone with more information is asked to contact officers at 604-717-2500 or call Crime Stoppers anonymously at 1-800-222-8477 (TIPS).

With a report from CTV Morning Live's Sheila Scott