Officers went to Seton Medical Center at about 2:30 a.m. after hospital officials contacted police to report the arrival of four victims of an apparent stabbing, Daly City police Sgt. David Mackriss said.
All four victims had moderate injuries, Mackriss said, none of which appeared to be life threatening.
The initial investigation led police to Serra Bowl based on information from one of the victims who said the stabbing took place there, Mackriss said.
Police found no evidence the stabbing took place at the bowling alley, Mackriss said.
Investigators now believe the stabbing occurred in San Francisco, possibly in the Richmond or Sunset districts, Mackriss said.
Officers from the Daly City and San Francisco police departments are both investigating the incident.