A San Francisco-bound Greyhound bus carrying 46 passengers was struck from behind by a semi-truck early Thursday morning, injuring several passengers and shutting down a stretch of I-5 as crews worked to clear the road. ABC 30 reports that the driver of the big rig did not appear to be under the influence, and may have fallen asleep at the wheel.

"Investigating officer already talked with, and evaluated the driver," CHP's Jay Adams told the channel. "It sounds like an unfortunate accident. Fortunately not a lot of people were hurt in it — at this point, it's minor."

The collision occurred around 4:40 a.m. near Kettleman City in the Central Valley, and for a time traffic was backed up on I-5 for miles. The semi-truck tipped on its side, and the bus was sent up on an embankment.

According to CBS 5, 3 people were hospitalized after the wreck. The two injured passengers and truck driver were taken to Coalinga Regional Hospital, and their injuries have been reported as minor. The uninjured passengers were temporarily stranded on the roadside before being picked up and taken the rest of the way to SF.

A similar crash involving a Greyhound bus occurred on Highway 101 in January, but in that tragic incident two people lost their lives.

Related: Five Dead In Early Morning Bus Crash In Merced County