An oil rig that was burning in the Gulf of Mexico for more than a day after an explosion has sunk, the U.S. Coast Guard said Thursday.

Lt. Cmdr. Cheri Ben-Iesau of the Coast Guard announced this latest development as an aerial search resumed for 11 workers who have been missing since the explosion on the rig Tuesday night off the Louisiana coast.

Crude oil was leaking from the rig at the rate of about 8,000 barrels per day, Coast Guard Petty Officer Ashley Butler said. The Coast Guard also is preparing for possible leaks of up to 700,000 gallons of diesel fuel but can do little to protect the environment until the fire is out, Butler said.

An investigation was under way to determine what caused the blast about 10 p.m. Tuesday aboard the Deepwater Horizon oil rig.

The rig was about 52 miles southeast of Venice, Louisiana, said Coast Guard Senior Chief Petty Officer Mike O’Berry.

“It obviously was a catastrophic event,” O’Berry said.

There were no indications it was a terrorist incident, the Coast Guard said.

Officials said 126 people were on board at the time of the explosion.

Of the 115 accounted-for workers, 17 injured were evacuated by helicopter from the rig. Ninety-four others were taken to shore with no major injuries, and four more were transferred to another vessel, according to the Coast Guard.

It was not known whether the missing workers were able to make it to one of the rig’s lifeboats — fully enclosed, fire-resistant vessels designed to evacuate people quickly.

The Coast Guard said favorable weather conditions and warm Gulf waters increase the likelihood of survival for the missing workers.

A federal lawsuit was filed Wednesday in New Orleans, Lousiana, alleging the companies connected to the oil rig explosion were negligent. The suit was filed on behalf of one of the 11 missing men.

Transocean Ltd., which owns the rig, and BP PLC, which operates the license on which the rig was drilling, were named as defendants.

A spokesman for Transocean did not immediately return a call requesting comment on the suit.

The suit says Shane Roshto of Amite County, Mississippi, “was thrown overboard as a result of the drilling explosion, and his body has not yet been located.”

His wife, Natalie Roshto, also is named as a plaintiff.

Carrol Moss told CNN affiliate WWL-TV in New Orleans that her husband had been rescued from the rig. But she said she had some anxious moments before receiving the call.

“The only thing I was thinking is, ‘How am I going to tell my kids that their dad is not coming home?’ ” Moss told the affiliate. “The worst goes through your mind. We were just blessed we got the call.”

Adrian Rose, a vice president for Transocean, said Wednesday that “we are deeply saddened by this event. Our thoughts and prayers are with the crew members of the Deepwater Horizon and their families.”

Transocean’s website describes the company as the “world’s largest offshore drilling contractor” with 140 offshore drilling units.

The rig involved in the explosion — a mobile unit that moves to different locations in the Gulf of Mexico — had been drilling for oil in its current spot since January, said Eileen Angelico, a spokeswoman for Minerals Management Service, the U.S. Department of the Interior agency that regulates the oil industry in federal waters.