The third attempt to seal the leaking gas well in Southwest China's Chongqing Municipality was launched on Thursday after the second attempt failed late on Wednesday.

Experts dealing with the accident said they decided to fill a type of sticky gel into the leaking layer, and then seal off the well with alumina cement.

There is one ton of the gel in stock at the site and three tons being transported from the neighboring Sichuan Province.

Li Yizhong, director of the State Administration of Work Safety,Jiang Jiemin, vice president of the well's owner China National Petroleum Corporation (CNPC), more than 50 experts, and over 800 workers are busy preparing for the effort.

It is expected that the sealing will finish in the early hours of Friday morning and the effects will be seen in three hours.

The second campaign to seal the Luojia No. 2 well in Gaoqiao Town of Kaixian County stopped on Wednesday night as the 524-meter-long drilling machine broke deep inside the well due to strong corrosive hydrogen sulphide, said Yang Qingli, a CNPC official.

Bubbles can be seen in the river adjacent to the leaking gas well, and burning sites are scattered in the riverbank and nearby hills. The leak can also be spotted around some local households.

The local government has warned people on the lower reaches not to drink water from the river. Gas workers are monitoring the river.

The well, with a depth of some 3,400 meters, began leaking around 7 a.m. on Saturday during final tests which were being conducted to bring the recently-completed well into production.

Some 15,000 local residents living around the leaking gas well have been evacuated.

No injuries have been reported from the incident. Workers have been burning off poisonous gas escaping from the well to prevent it collecting.