Six were shot by a fellow passenger aboard a Greyhound bus travelling through California early Monday, reports said.
Gunfire erupted shortly before 1:30 a.m. as the bus was headed north on Interstate 5 near Lebec, CNN reported, citing the California Highway Patrol.
The shooting victims were all rushed to area hospitals. Their conditions were not immediately known.
Authorities said that the shooter was among the roughly 40 passengers on the bus, which was travelling from Los Angeles to San Francisco at the time, according to the news outlet.
The suspect, whose identity was not immediately released, was taken into police custody.
The motive for the shooting was not immediately clear.