BEIJING (AFP) - Chinese police launched a criminal investigation on Saturday into a horrific bus blaze that claimed the lives of 47 people, and identified a suspect in connection with the inferno.

While stopping short of saying they believed the fire had been started deliberately, authorities announced that the fire, which engulfed the bus in minutes during evening rush hour in the southeastern city of Xiamen, was being treated as a "criminal case".

City officials told a news conference the criminal probe was launched after initial investigations showed the accelerant was petrol, while the bus was equipped with a diesel engine.

The investigation by experts and police also showed that the tyres and tank of the bus "remained complete", Xinhua said.

A "suspect has been identified", a message posted by Xiamen police on its verified page on Sina Weibo, China's version of Twitter, said.

A 59-year-old man's apartment had been searched and some items were taken away by police, the Tencent news website said.

There were no further details on the police investigation, but Xinhua reported that bus station staff were making "strict safety checks on passenger's luggage" on Saturday.

In 2009, a bus in China's southwestern city of Chengdu was set ablaze by an unemployed man with gasoline, killing 28 people and injuring more than 70.

There has been previous reports of attacks on public transport in China, by people aiming to air personal grievances or settle scores with authorities.

About 100 people were on the Xiamen bus when it caught fire - China's deadliest transport accident in recent years.

Xinhua said 34 people were hospitalised following the blaze on the BRT (Bus Rapid Transit) vehicle.

Witnesses said the bus was destroyed within 10 minutes by the fire, and some heard a series of explosions.

Ms Jiang Xiatong, who was sitting near the back window of the bus, told the state-run Global Times newspaper that she smelt a "peculiar odour" before the vehicle caught fire.

"While I was climbing, I felt my legs being pressed by someone, and then I felt a hot wave burn my legs," she told the newspaper.

The bus operated on a 9 metre elevated road, in what was believed to be China's first overhead rapid transport system when it was launched in 2008.

The network of three lines covers 67 km, and carries 265,000 people a day, with buses often crowded during rush hour.

Scores of netizens took to the Internet to raise concerns following the blaze.

The Xiamen fire comes after a crash involving two high-tech bullet trains in the eastern province of Zhejiang in 2011 sparked public debate that officials were overlooking safety in their rush to develop the country's vast transport network. More than 40 people died in that accident.

Later that year, a collision on a new subway line in the economic hub of Shanghai that injured hundreds of people, also raised questions over commuter safety.

"This is the side-effect of developing too fast," said one netizen on Sina Weibo after the Xiamen bus blaze.

"I'm nervous every time taking the BRT."

Another said: "How many lessons of blood does this country need to learn before it recognises its quality problem?"