WILLOW BEACH, Ariz. (AP) — A charter bus carrying tourists back to Las Vegas from the Grand Canyon crashed on an Arizona highway, killing the driver and injuring more than 20 passengers, six of them seriously, authorities said.

The bus was northbound on Highway 93 on Friday night, nearing the Nevada state line, when the driver suffered a physical problem and lost control, the Arizona highway patrol said. The company that offered the tour said the driver may have suffered a heart attack.

The vehicle hit a ravine, tore up a small hill, and then bounced and lurched over rough terrain for more than 700 feet before stopping, damaging the front end but remaining upright, patrol spokesman Carrick R. Cook said.