The bubbles popping up in Lake Peigneur are explosive but apparently natural, says a leader of the group trying to stop expansion of a natural gas storage operation under the lake.

Tests by the U.S. Geological Survey show the bubbles are 70 percent methane and 30 percent air, with more than double the oxygen needed for a volatile mix, said Nara Crowley, vice president of Save Lake Peigneur. She said that doubles both the chance of explosions and the power of any that might occur.

She said the bubbles come up near the wellhead owned by AGL Resources of Atlanta, which wants to scour out new caverns in the vast salt dome under the lake to double its natural gas storage.

That proximity, Crowley said, probably increases the danger of fire and explosions.

The samples were taken in October, and results of tests from samples taken Dec. 18 should be available in the next couple of months, Crowley said.

She said the study indicated that the methane was probably from a naturally occurring source rather than AGL's caverns, but also that something is putting the gas under pressure to push it to the surface with such a high air content.

Nobody yet knows the cause, She said no one has answers yet for the cause. Her group will meet in January to consider the test results and decide what to do next.

Save Lake Peigneur has been trying to stop Jefferson Island Storage and Hub, an AGL subsidiary, from creating new storage caverns. In addition, the state contends that AGL's lease has lapsed, a question currently in court.

Lake Peigneur, near Delcambre on the boundary of Vermilion and Iberia parishes, drained into the salt dome in 1980 when an oil drilling rig punched into a working salt mine.

The local group has said that the intermittent bubbles might indicate a problem with the existing natural gas storage caverns or the salt dome surrounding them.

AGL officials have maintained that the operation is safe, that the U.S. Department of Energy has found salt domes the safest places to store natural gas and that the company's local employees also have a vested interest in making sure nothing goes wrong.