A bus plummeted nearly 1,000 feet off a cliff and crashed Tuesday into a river in a mountainous region, killing 24 people, police said. At least 25 survivors were hospitalized with injuries.

More people may be trapped underneath the bus, which was lying upside down in shallow water near Matatiele in the Eastern Cape, said police spokeswoman Zandra Wiid.

The accident occurred around 10 a.m. when the privately owned bus, believed to be carrying 80 passengers, plummeted off the cliff and into the river, Wiid said.

The cause of the accident wasn't immediately clear. Windy conditions delayed the rescue effort, she said.

The dead included three children, ages 1, 3 and 7, Wiid said.