MEXICO CITY (July 20, 2012)—A bus that was headed to a beach in western Mexico went off a cliff, killing at least 21 people, Mexican authorities said.

Nayarit state government spokesman Sergio Canedo says another 29 people were injured in the accident Friday in the town of Tequepexpan.

Canedo says the passengers were vacationers from the northern state of Chihuahua who were heading to Guayabitos beach on Nayarit's coast.

Canedo says investigators are still trying to determine what caused the bus to veer off the road.