An intercity bus veered off a road in western Russia, killing four people and injuring another 11, authorities said Friday.

The bus driving from Moscow to Volgograd veered into a ditch and overturned in the Ryazan region, about 250 kilometers (155 miles) south of Moscow. At least four people, including the bus driver, died and at least 11, including several children, were hospitalized with injuries after the overnight crash, authorities said.

Police said the driver may have lost control of the bus after falling asleep.