At least 25 people are dead and dozens hurt after a natural gas-powered commuter bus burst into flames in southwestern China.

Witnesses in the city of Chengdu say the bus did not explode, but burned quickly.

The accident happened during the morning rush hour, and the bus was packed with commuters.

Government officials say 76 people were injured -- more than two dozen seriously.

People nearby rushed to break the sealed, air-conditioned bus windows, allowing some to escape with minor injures.

A government report says the cause is under investigation.