An explosion Thursday on a Gulf of Mexico oil platform thrust the politics of offshore drilling back in the spotlight, as critics immediately seized on the accident to highlight what they called the industry's inherent dangers.

The explosion and fire happened Thursday morning at a production platform at Vermilion Block 380, about 100 miles off the Louisiana coast, according to its owner, Houston-based Mariner Energy, Inc.

That's west of where the Deepwater Horizon rig exploded in April, killing 11 workers, setting off one of the worst environmental disasters in U.S. history and leading to protracted debate on Capitol Hill over the merits and safety of offshore drilling.

No one died in this incident - all 13 crew members were rescued - and there were conflicting reports on whether it had caused a spill, though nothing as serious, apparently, as the one BP is now cleaning up.

One Coast Guard report said a sheen about a mile long and 100 feet wide was spotted in the area, but the company indicated an initial flyover showed no evidence of a "hydrocarbon spill."

Energy Committee Chairman Henry A. Waxman (D-Calif.) and the chairmen of that panel's oversight and energy subcommittees - Bart Stupak (D-Mich.) and Edward Markey (D-Mass.) - sent a letter to Mariner Energy on Thursday requesting a briefing on the incident and its possible causes by Sept. 10.

Mariner's production platform is located in about 340 feet of water, according to numerous press reports, which are relatively shallow depths. The Deepwater Horizon rig, by contrast, was operating in 5,000 feet of water.

Still, the accident quickly prompted calls from environmentalists and some Democrats to continue the temporary federal moratorium on deepwater drilling imposed because of the BP spill.

The Obama administration has been under intense pressure from the oil industry, Republicans and Gulf Coast lawmakers from both parties to lift the ban before its scheduled Nov. 30 expiration. White House and Interior Department officials have said in recent weeks that they're open to cutting the ban short if they're confident drilling can proceed safely.

Markey, a senior member of the Energy and Commerce Committee and a consistent critic of BP, said on Thursday: "This explosion highlights the significant risks associated with offshore drilling, and that much is left to be done to keep America's workers and waters safe from those risks."

"This is not a situation we could afford to ignore before the Deepwater catastrophe, let alone today," said Rep. Raul Grijalva (D-Ariz.), the co-chair of the Congressional Progressive Caucus. "It seems that everyone is content to let another oil rig explode every few months rather than taking concrete steps to clean up the industry."

Oceana, an environmental group that opposes offshore oil-and-gas development, also quickly called the accident evidence that the federal ban on deepwater drilling should not be lifted early.

"This latest rig explosion underscores the need for the U.S. to maintain its moratorium on all new offshore oil and gas drilling. It's another reminder that drilling accidents happen all too frequently. We cannot afford to lose any more human lives, nor can we tolerate further damage to the Gulf and its irreplaceable ocean ecosystems," Oceana senior campaign director Jacqueline Savitz said in a statement.

The Sierra Club noted this is the "second incident in recent months that has sent oil workers into the water, and some of them have never returned."

"The oil industry continues to rail against regulation, but it's become all too clear that the current approach to offshore drilling is simply too dangerous," executive director Michael Brune said in a statement. "We don't need to put American workers and waters in harm's way just so multinational oil companies can break more profit records."

At a mid-afternoon press briefing, Louisiana Gov. Bobby Jindal (R) said the fire on the platform was still burning, but that the company reported it was "nearly burned out."

Sen. David Vitter (R-La.), who also opposes the moratorium, tweeted Thursday of reports that "all survived explosion in Gulf, and wasn't an active well. Hope that's the case. Keeping all in thoughts and prayers."

The National Ocean Industries Associaton, a trade group, countered the fresh attacks on offshore development with a call Thursday afternoon to "keep things in perspective."

"Any accident in the offshore energy industry is certainly worthy of attention, whether it be as minor as a trip and fall or something resulting in serious injury. The good news is that today, there was no loss of life. But coming just 4 months after the Macondo well accident, today's incident hits everyone's radar," said Radall Luthi, the group's president, who led the Interior Department's offshore drilling agency under former President George W. Bush.

"While we do not yet know the cause of today's accident, we must keep things in perspective, and remember that accidents happen in almost any occupation. We should also remember that oil and gas is vital to our economy and everyday lives," he said.

The company said in a statement the cause of the explosion was unknown and is under investigation.

The New York Times, citing federal records, said there have been at least four accidents on the platform - including two fires - since 2000.

Jordan Fabian and Elise Viebeck contributed.