Around 7,000 people have been evacuated from the surrounds of a deadly oil-well explosion in northeast India, authorities said Thursday, as environmentalists warned local wildlife was being hit by contamination.

Oil India engineers have been battling since May 27 to cap a blowout that this week ignited a huge ball of fire in Tinsukia district of Assam state.

Company officials said around 7,000 people living nearby have now been evacuated, after some 2,500 local residents were originally ordered out.

On Thursday the fire was still raging, and jet-black smoke could be seen billowing into the sky from kilometres (miles) away.

The Baghjan oil field is adjacent to the Dibru Saikhowa National Park and the Maguri-Motapung wetlands that are home to several endangered species including tigers, dolphins and elephants.

"The Dibru river is full of dead fish. A thin film of oil has covered the river," local environmentalist Nirantar Gohain told the Times of India daily.

Environmentalists have warned of the danger of a catastrophe at the site of an Indian oil well explosion
Environmentalists have warned of the danger of a catastrophe at the site of an Indian oil well explosion AFP / Biju BORO

"Two days ago, Gangetic dolphins floated up".

Villager Kuhima Moran Das said he and his family ran for their lives after the initial blast.

"Now we cannot sleep at night, we cannot eat," he told AFP. "How can we survive."

Two firefighters have been killed battling the blaze, including local hero Durlov Gogoi, who had represented Assam state at junior football.

Oil India warned Wednesday it could take a month to cap the leak.

The Press Trust of India said officials had called in experts from Singapore, the United States and Canada to help tackle the fire.

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