NANJING - An explosion toppled a building in East China's Jiangsu province on Tuesday morning, killing at least six people, according to local authorities.

Firefithers work to carry a person out of the debris after an explosion-triggered collapse of a building in Suzhou city, East China's Jiangsu province on June 11, 2013. [Photo/CFP]

Nine others have been hospitalized, and three of them are in critical condition. Several people are still buried under the rubble of the three-story building.

The explosion occurred around 7 am in the city of Suzhou, an industrial hub in the Yangtze River Delta.

A preliminary investigation showed that the blast was caused by a gas leak.