The state Department of Natural Resources sent field agents to Lake Peigneur in Iberia Parish on Thursday to investigate reports of bubbling at the lake, where natural gas is stored in massive underground caverns scoured out of a large salt dome.

Residents in the area have reported sporadic bubbling in the past and have raised concerns that similar bubbling was observed in the Bayou Corne area in northern Assumption Parish before a large sinkhole developed there last year.

The Bayou Corne sinkhole is believed to be related to the collapse of a large underground storage cavern in a salt dome.

DNR spokesman Patrick Courreges said field agents did not directly observe bubbling at Lake Peigneur on Thursday but did see foam on the lake’s surface.

“We found foaming residue on the top,” he said. “... The foam is the result of something happening.”

Courreges said it is too early to speculate on what might be causing the bubbling and that DNR will follow up on any future reports in an attempt to determine the cause through observation and testing of gas or other substances in the bubbles.

Save Lake Peigneur President Nara Crowley said residents have observed 79 instances of bubbling at the lake since 2006.

The group has been fighting a plan to expand natural gas storage operations under the lake.

Crowley said the latest instance of bubbling seems to have gone on longer than any other episode, with bubbles observed for several hours on Wednesday and on Thursday morning.

She said that lines of bubbles stretched for a few thousand feet across the lake.

Prior tests at the lake have not identified the source or reason for the bubbling.

Atlanta-based AGL Resources, which owns the two natural gas storage caverns, has maintained the bubbles are not coming from the gas storage caverns and that tests have confirmed the stability of those caverns.

AGL is seeking permits to scour out two new salt caverns under Lake Peigneur.

The company’s plans have been met with vocal opposition from residents in the area and environmental groups.