Residents of Gaoqiao, a town in Southwest China's Chongqing Municipality, received a rude awakening on Saturday morning when a gas leak triggered a massive explosion.

There were no injuries resulting from the blast at the gas well, which caused the evacuation of more than 5,000 local residents, reported Xinhua News Agency.

Residents of Gaoqiao, a town in Southwest China's Chongqing Municipality, watch the raging flames of a gas leak on Saturday night March 25, 2006 as they leave their homes. [Xinhua]

Local residents reported hearing a "big bang" at around 5 am and said the nearby river was "rolling and foaming."

After being evacuated, local residents were warned against drinking water from the river. Tests revealed the water contained methane, possibly one of the gases in the well. Workers ignited gas at the mouth of the well on Saturday to avoid the possibility of a build-up and an explosion. They tried to shut down the well yesterday but this proved very difficult.

"Gas leaked from the No 2 well. However, the No 2 well is connected to the No 1 well, bringing us problems when we tried to stop the leak," an employee of the Chuandong Drilling Company told the Chengdu-based West China Metropolis Daily.

Chen Caifan, a local government official in charge of the emergency team, told Xinhua that a pipeline broke at the No 2 well on February 7. Although construction of the well had just been completed, it had yet to become operational.

The massive leak took place on Saturday, following Friday's failed attempt to shut it down.

Tragedy struck the same area in December 2003, when a leak caused the deaths of 243 people one of the country's worst industrial accidents.

That leak spewed a deadly cloud of natural gas and hydrogen sulphide over a 25 square-kilometre area. Many residents died in their sleep or collapsed while trying to flee.

About 9,000 people were hurt and more than 41,000 villagers were forced from their homes. Many survivors suffered lung damage and burns to their eyes and skin.

Six employees of the Chuandong Drilling Co were sentenced to prison in 2004 for negligence. The same company was operating the 3,400-metre deep well in the latest incident, Xinhua said.