The fire Thursday at an oil platform off the Louisiana coast may not, in the end, do much harm to the Gulf of Mexico. But it could still mean trouble for both the Obama administration and the oil industry -- by raising new questions about the gulf's oil fields.

The industry and the White House have battled each other all summer over a six-month moratorium on deepwater oil drilling imposed by the Obama administration after the historic spill from the Deepwater Horizon rig.

But, within that fight, there was common ground: Both sides seemed to agree that there was less of a crisis among the gulf's other rigs. That would include those in shallower water, less than 500 feet deep, and those platforms that merely pumped oil instead of drilling for it.

Then, on Thursday, a shallow-water pumping platform caught fire.

In the hours afterward, the White House and the American Petroleum Institute offered little comment. But others -- in Congress and in environmental groups -- rushed out statements that raised wider questions about oil safety.

"This is a shallow-water platform, and that's the key here. Since the beginning of this crisis, the Obama administration has attempted to limit the crisis to deep-water drilling and to suggest that shallow-water oil drilling is safe," said Kieran Suckling of the Center for Biological Diversity, an environmental group. "I'm not in the least bit surprised."

The Coast Guard and the platform's owner, Houston-based Mariner Energy, said they had not determined what led to the fire. Experts said that if it had not happened in this place, during this summer, it might have attracted little notice: Last year, for instance, there were 133 fires or explosions on rigs in the Gulf of Mexico.

"This appears to be an industrial accident. Little or no pollution. In shallow waters," said Eric Smith, associate director of the Tulane Energy Institute in New Orleans. "There is very little here that is analogous to the Deepwater incident."

But, at this touchy moment, the differences between the two accidents could be precisely the point. The Deepwater Horizon blast had contradicted promises from Mr. Obama and the oil industry that offshore drilling was safe. Thursday's fire threatens to undermine confidence that most drilling is still safe, outside of the harder-to-plug wells in very deep water.

"What it does bring to light is that there are risks with oil and gas production ... that are associated with activities that go beyond deepwater drilling," said Donald F. Boesch, president of the University of Maryland Center for Environmental Science and a member of a presidential commission charged with learning the lessons of the BP spill.

On Capitol Hill, three top Democrats on the House Energy and Commerce Committee sent a letter to Mariner Energy, requesting a briefing on Thursday's accident.

In May, the Obama administration imposed the six-month moratorium, which effectively stops all new drilling in water deeper than 500 feet. The administration has said technology makes shallow-water leaks easier to plug.

But accidents happen in both deep and shallow water. In 2007, for instance, a journal article written by federal regulators found that 80 percent of 15,077 gulf wells were in 500 feet of water or less. And, between 1992 and 2006, these accounted for roughly the same ratio of "blowouts," a kind of accident where oil and gas shoot uncontrolled to the surface, as deep-water wells.

The oil industry has blasted the moratorium as economically crushing. On Wednesday, the oil lobby held a "Rally for Jobs" in Houston. Among those in attendance, according to a Financial Times report, was Mariner official Barbara Dianne Hagood.

Federal records show that Mariner has a history of alleged safety violations. In June, Mariner Energy paid a $20,000 federal fine for an alleged regulatory violation on an offshore platform, according to government records. The platform's heliport was taken out of service as a result of a fire, leaving a boat landing as the only access to the structure, and inspectors found that the boat landing's grating was corroded, and its handrails were missing.

In May, Mariner Gulf of Mexico LLC paid a $35,000 fine for allegedly taking inadequate steps to control hydrogen sulfide pollution, according to the Bureau of Ocean Energy Management, Regulation and Enforcement's website.

Including Thursday's fire, Mariner has now had 16 fires at its offshore facilities since the beginning of 2007. Most were minor, federal records indicate.

Mariner spokesman Patrick Cassidy said in an e-mail Thursday: "We believe the outcome today, where no one was injured, is an example of learning from past mistakes and having good procedures in place. Proper procedures were followed. No one was injured today, and no oil spilled from the wells."

Washington correspondent Daniel Malloy writes the "Pittsburgh On The Potomac" blog exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.