Most of those taken to hospital were children

At least 191 people died after inhaling toxic fumes following an explosion at the field in Chongqing municipality.

Hundreds of others flooded into local hospitals suffering from poisoning and chemical burns.

Government officials have arrived at the scene to investigate the disaster and engineers are working to try to seal the blown-out well.

Natural gas and sulphurated hydrogen were released by the blast

Rescue workers are searching surrounding villages for more victims.

President Hu Jintao has ordered local authorities to do everything possible to speed up the rescue and prevent the poisonous gases from spreading.

Ninety-five thousand people have died in work-related accidents in China in the first nine months of this year.

'Patients everywhere'

Most of the victims died immediately after a well at the field burst and released a cloud of poisonous gases.

A nearby hospital was overwhelmed as it tried to deal with victims of the blast.

Go all out to rescue victims, prevent poisonous gas from spreading further and reduce casualties President Hu Jintao In pictures: Gas blast

"We are very busy. There are patients everywhere," one unnamed hospital worker told the Reuters news agency.

Almost 300 people, mostly children, were reported to be receiving treatment in hospital, and 10 times that number are thought to have suffered minor symptoms.

The injured were reported to have swollen and sensitive eyes, and some found it difficult to stand, local media reported.

By the end of the day, 41,000 people had been evacuated from within a radius of five kilometres (three miles) of the field.

Operations were going normally before the gas suddenly exploded from the side of the drill, Qian Zhijia, deputy head of the gas field, told Xinhua news agency.

The accident sent a high concentration of natural gas and sulphurated hydrogen shooting 30 metres (100 feet) out of a burst well.

Mr Qian says the situation should be under control by Friday.

China is notorious for its dangerous working conditions.

Cabinet response

Beijing has sent a team led by a cabinet secretary to the scene, Xinhua reported.

It said President Hu and other Chinese leaders had called on local authorities to "go all out to rescue victims, prevent poisonous gas from spreading further and reduce casualties".

They urged local officials to accommodate the thousands evacuated.

The natural gas industry is an emblem of modernisation in a country heavily dependent on coal, our correspondent says.

The field belongs to the China National Petroleum Corporation.

A company spokesman said 13 special rescue vehicles were en route to the scene and that mud would be pumped into the hole to stop the spread of toxic sulphurated hydrogen.

Fires have been lit to try to burn off leaking gas, AFP news agency reported.