NEW ORLEANS - Fifteen people were injured, including seven critically, and 12 others were missing Wednesday after an explosion that left an offshore drilling rig tilting and on fire in the Gulf of Mexico.

Helicopters, ships and an airplane were searching the waters off Louisiana's coast for workers who are believed to have gotten off the rig, but are unaccounted for.

Most of the 126 people on the rig, called Deepwater Horizon, were thought to have escaped safely after the explosion at about 10 p.m. Tuesday, Coast Guard Senior Chief Petty Officer Mike O'Berry said.

 

However Coast Guard spokeswoman Katherine McNamara told msnbc.com that a total of 15 had been injured, seven critically. Another 12 were still unaccounted for, she said.

Two of the injured were taken to a trauma center in Mobile, Ala., where there is a burn unit, but the nature of their injuries was unclear, Coast Guard Lt. Sue Kerver said.

 

'Burning pretty good'
The rig, about 52 miles southeast of Venice on Louisiana's tip, was listing about 10 degrees and still burning Wednesday morning.

Video   Fire engulfs rig   April 21: Coast Guard rescues workers from the Deep Horizon. msnbc tv

"It's burning pretty good and there's no estimate on when the fire will be put out," O'Berry said.

O'Berry said many workers who escaped the rig were being brought to land on a workboat, while authorities searched the Gulf of Mexico for any signs of lifeboats and the missing workers.

"We're hoping everyone's in a life raft," O'Berry said.

O'Berry said at one point the fire was so large and intense that it was hampering rescue efforts, WWL TV reported.

 

Fatalities feared
The rig was drilling but was not in production, according to Greg Panagos, spokesman for its owner, Transocean Ltd., in Houston. The rig was under contract to BP PLC.

Transocean via AP The rig Deepwater Horizon rig is seen in an undated file photo.

"As far as we know there have been no fatalities, but this could change," Panagos was quoted as saying by the website Upstreamonline.com.

"A substantial majority of the 126 member crew is safe but some crew members remain unaccounted for at this time," the company also said in a statement.

"Injured personnel are receiving medical treatment as necessary," the statement added. "The names and hometowns of injured persons are being withheld until family members can be notified."

BP spokesman David Nicholas said all six BP personnel who had been on the rig were safe.

Kerver said the Coast Guard and the federal Minerals Management Service will work together to investigate possible causes of the accident.

"It's still too early to tell the cause," Panagos said. "Our focus right now is on taking care of the people."

The Coast Guard statement included a next-of-kin hotline number, (832) 587-8554.

O'Berry said Coast Guard environmental teams were on standby in Morgan City, La., to a****s any environmental damage once the fire was out.

 

Rig floats using pontoons
According to Transocean's website, the Deepwater Horizon is 396 feet long and 256 feet wide. The semi-submersible rig was built in 2001 by Hyundai Heavy Industries Shipyard in South Korea. The site is known as the Macondo prospect, in 5,000 feet of water.

The rig is designed to operate in water depths up to 8,000 feet and has a maximum drill depth of about 5.5 miles. It can accommodate a crew of up to 130.

The rig is floated to drilling sites, and has pontoons and a column that submerge when flooded with seawater. The rig doesn't touch the sea floor, but sits low in the water, where it is moored by several large anchors.

Last September, the Deepwater Horizon set a world deepwater record when it drilled down just over 35,000 feet at another BP site in the Gulf of Mexico, Panagos said.

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

Panagos did not know how much the rig cost to build, but said a similar rig today would run $600 million to $700 million.