Details have been slow to emerge in a weekend stabbing the San Francisco Police Department says occurred on a Muni bus.

According to the "official Twitter of SFPDnightWatch," as of 9:31 p.m. Saturday, police were investigating a stabbing on a Muni bus, as you can see from the tweet and photo above.

The stabbing occurred on the 2000 block of Market Street, police say, which is located between Dolores and Church Streets, and is perhaps best known as the location of the no-longer-24-hour Safeway at Church and Market.

Based on the photo shared by SFPD, it appears that the stabbing occurred on the J/N shuttle bus, a transit line running during Muni Metro's scheduled night and weekend shutdown as the transit system tests its new trains.

As of publication time, police had yet to release additional information on the circumstances of the crime, or on the suspect or victim. When that information is made available to the public, this report will of course be updated.

Related: Entire Muni Subway Is Closing Nights And Weekends For Four Weeks To Test New Trains