Police found four victims in the vicinity of Hyde and Eddy Streets in the Tenderloin district, according to local Fox affiliate KTVU.
Officers found the four victims at approximately 5:25 a.m. local time. The victims reportedly told police that a man approached them, took out a knife, and started stabbing them.
After police administered treatment at the scene, medics responded and transported all four victims to a hospital. One reportedly suffered life-threatening injuries, while the other three had more minor, non-life-threatening injuries.
Police have not provided any information about a suspect and those with knowledge of the situation are encouraged to contact the SFPD.
Violent crime has been an ongoing problem in California in general and San Francisco in particular. During her "State of the City" speech March 9, San Francisco Mayor London Breed, a Democrat, acknowledged that the progressive city had been plagued by rampant vandalism, car and home break-ins, drug use, and gun violence.
"Too many people across the city don’t feel safe," Breed said.
The mayor went on, however, to downplay crime reports as "noise" from "right wing media" outlets.
"You know, there’s a lot of noise about what’s happening in our city. You see it in the headlines, often in the right-wing media," the mayor said. "They love to talk about San Francisco, don't they? You see it on social media. You see one video take off as if it's telling the whole truth about who we are. I know it’s challenging with all that noise to really understand what’s happening."
Fox News' Kristine Parks contributed to this report.