Police are investigating a shooting that took place on a busy highway in San Francisco early Monday morning, CBS San Francisco reported.

The story is still developing, but here’s what we know so far:

A Sig-alert was issued at 3:23 a.m. due to the closure and traffic is being diverted off the highway at Alemany Boulevard, CHP officials said.

The California Highway Patrol reports that there were “several victims” in the shooting on Interstate 280 but there was no word on their conditions. All southbound lanes were closed.

The CHP reported that the southbound lanes of I-280 would be closed for about two hours.

Police estimate that there are between three and six victims.

The investigation has led CHP officials to shut down southbound Interstate Highway 280 at Alemany Boulevard.

Lanes are expected to be closed until at least 7 a.m.