US Coast Guard is searching the Gulf¹ of Mexico for at least 11 oil workers missing after an explosion and fire on an off-shore drilling platform.

美国墨西哥湾某钻井平台发生爆炸事故，海岸警卫队正在出事海域搜寻失踪的11名油田工人。

The Deepwater Horizon rig（钻探设备） was still burning hours after the blast on Tuesday night, 84km (52 miles) south-east of the Louisiana port of Venice.

Seventeen of the 176 workers were evacuated²（疏散，排空） by air and sea on Wednesday. Another 98 were later rescued by boat.

The rig is reportedly tilting³（倾斜） about 70 degrees and threatening to topple over.

Its operators, Transocean, said there had been no signs of trouble before the explosion and crews had been doing routine work.

A spokesman for the Switzerland-based contractor⁴, Greg Panagos, said the rig had been drilling at the time but was not in production.

The cause of the blast is still unclear. "Our focus right now is on taking care of the people," Mr Panagos added.

'Burning pretty good'

A day after the explosion on the Deepwater Horizon, Coast Guard spokesman Mike O'Berry said four helicopters, four Coast Guard boats and a plane were helping⁵ search for the missing workers.

"We're hoping everyone's in a life raft（充气救生船） ," he added.

The Coast Guard said 17 workers had been evacuated by air and sea on Wednesday morning, three of whom were critically injured. The other workers were later picked up by boat and are expected ashore⁶ later on Wednesday.

Fire boats were still battling the fire on the rig.

Deepwater Horizon was drilling for BP on part of the Mississippi Canyon⁷ Block 252 known as the Macondo prospect⁸, in 1,500m (5,000ft) of water.

Built in 2001 by South Korea's Hyundai, the semi-submersible（能潜水的） rig is 120m (396ft) long and 78m (256ft) wide, according to Transocean.

A semi-submersible rig floats above a drilling site and does not touch the sea floor.

Able to operate in up to 2,400m (8,000ft) of water, Deepwater Horizon set a world record in September for the deepest oil and gas well when it drilled down 10,685m (35,055ft) at another BP site in the Gulf of Mexico.

"It's one of the more advanced rigs out there," Mr Panagos said.