ISTANBUL — A tour bus tipped over Saturday on a serpentine mountain road in Turkey, killing 24 people as it fell off a cliff and hit a car, Turkish authorities said.

The governor of Mugla province, Amir Cicek, said the driver is among the dead and the accident may have been caused by a failure in the bus’s braking system. He said investigations were continuing to determine the exact cause.

Cicek said the bus flipped over on a bend in the road and fell 15 meters (50 feet) down a cliff as it was traveling from the coastal province of Izmir to Marmaris, a popular tourist destination.

He said 10 people remain in critical condition and all the passengers were Turkish.

The deputy governor of Mugla province, Kamil Koten, told Turkey’s state-run Anadolu news agency that most of those killed were women.

Anadolu said the bus was in a convoy of six, carrying mostly women and children for a Mother’s Day event.