VANCOUVER -- Police say a weekend knife fight that left four men injured was between two Metro Vancouver gangs.

The fight broke out shortly before 2:30 a.m. Sunday, and involved about 20 people, police said the next day.

"The gangsters had an altercation inside a Yaletown establishment which spilled onto the street," Vancouver Police Sgt. Aaron Roed said in a statement Monday.

Officers did not say what started the fight, nor did they say which gangs were involved in the fight.

Four men were taken to hospital for treatment for stab wounds, and one remained in serious condition Monday.

Roed said the men's lives were saved by members of the VPD's Emergency Response Team, who'd been called to the scene and were trained in what the department calls "tactical emergency medical services."

Seven people were arrested and taken to jail following the fight. The VPD said Monday that they'd all been released without charges.

The investigation is ongoing and officers expect that those involved will be charged at some point.

Meanwhile, investigators are looking for cellphone video of the incident and information from witnesses.

Tips can be left with the VPD's Major Crime Section at 604-717-2541, or through Crime Stoppers anonymously.