Eleven workers are still missing after a massive explosion aboard an oil platform off the Louisiana coast.

In addition to the missing, 17 workers were injured — four critically — and evacuated to hospitals onshore. The remaining 111 people who were on the offshore platform “Deepwater Horizon” when the explosion occurred have been safely evacuated to Port Fourchon, La. They were checked by doctors before being brought to a hotel in suburban New Orleans to reunite with their relatives.

According to an Associated Press report, rescue crews had covered the 1,940-square-mile search area by air 12 times and by boat five times, by Thursday morning. Officials hoped the 11 missing workers might have been able to get to a covered lifeboat with enough supplies to survive for an extended period.

The rig, owned by Transocean Ltd., was under contract to oil giant BP and was doing exploratory drilling about 50 miles off the coast of Louisiana.

The 400-by-250-foot rig is roughly twice the size of a football field, according the Transocean’s website. After the explosion, a column of boiling black smoke rose hundreds of feet over the Gulf of Mexico. Officials said environmental damage appeared minimal so far.

Company officials said the explosion appeared to be a blowout, in which natural gas or oil forces its way up a well pipe and smashes the equipment. But precisely what went wrong was under investigation.

Workers typically spend two weeks on the rig at a time, followed by two weeks off. Offshore oil workers typically earn $40,000 to $60,000 a year — more if they have special skills.

Since 2001, there have been 69 offshore deaths, 1,349 injuries and 858 fires and explosions in the Gulf, according to the federal Minerals Management Service.

Source: The Associated Press