An AC Transit bus traveling on Fremont Street around 9:20 a.m. Wednesday crashed into several vehicles including another AC Transit bus, and the collision temporarily shut down the Fremont off-ramp from the Bay Bridge.

As ABC 7 reports, at least four people had to be taken to the hospital as a result of the crash, including the driver of the bus that caused it, and they note that a medical emergency may or may not have been occurring with the driver.

The bus ended up coming to a stop on a sidewalk, as you can see in photos. As NBC Bay Area reports, the crash also damaged a construction site at Fremont and Folsom Streets. Reportedly no one was injured on the second bus.

The tweet below from an NBC Bay Area reporter says that five people were injured including the driver, two bus passengers, and two people in another car that was hit. Another tweet confirms that the Fremont ramp reopened as of about 11:20 a.m.

The cause of the crash has yet to be determined.