An express bus burst into flames on an elevated roadway in southeastern China on Friday, killing at least 42 people and injuring 33 others, state media reported.

The blaze occurred during the evening rush hour in the prosperous port city of Xiamen, the official Xinhua News Agency said.

A local fire official who only gave his surname, Sun, said bodies were piled up inside the bus. He said the cause of the fire was being investigated.

Operations of the entire express bus system, known as Bus Rapid Transit, were suspended after the accident, Xinhua said. It quoted a survivor as saying she smelled gasoline and then saw a fire spreading rapidly.

Photos on Chinese social media showed huge clouds of black smoke rising from the burning bus. Victims were seen bleeding with torn clothes and burned skin.

An official news site, Xiamen Net, said witnesses heard sounds of explosions after the fire had been burning for about 10 minutes.

Xiamen's BRT system began operations in 2008. It covers more than 80 kilometers (50 miles) and carries more than 250,000 people each day. Xianmen Net said the buses are often crowded during rush hour.

China's public transit has been expanding rapidly over the past decade, but there are worries that the country is sacrificing safety in its rush to roll out modern services.

In 2011, a high-speed train accident near the eastern city of Wenzhou killed 40 people. Later that year, a collision on a new subway line in the financial hub of Shanghai injured hundreds of people.

In 2009, an unemployed man set fire to a packed bus in Chengdu, killing himself and 26 others.