CODY -- The Wyoming Department of Environmental Quality has released new information about the possible causes behind the spill of 2 million gallons of a gasoline-grade material in May at an oil refinery near Rawlins.

A number of factors may have contributed to the sinking of a floating roof on a storage tank at the Sinclair Oil refinery, according to a statement issued by the DEQ in response to a request by The Billings Gazette for more information on the spill.

The floating roof on a storage tank sank and punctured the tank floor, spilling approximately 2 million gallons of light virgin naphtha, a gasoline intermediate or blending stock, according to the statement.

Among the factors that the DEQ has found may have contributed to the roof failure were: leaks in the pontoon compartments that keep the roof afloat, possible accumulation of water and debris on the roof deck and overfilling the tank in the days prior to the spill.

The DEQ presented Sinclair representatives with the agency's findings on Tuesday, and the company will have a chance to respond before the DEQ issues a formal report on the incident.

The statement said that the agency "will pursue appropriate actions consistent with the evidence it has collected."

The company has released few details about the massive spill of highly flammable liquid since the May 3 incident, but officials have said containment berms kept the material from escaping the immediate area around the tank.

Monitoring wells installed inside the bermed area have detected contaminants in subsurface water, but the spill is not believed to be migrating outside the containment area.

The spill is one of several incidents at the refinery in recent months that have attracted public attention, prompting local officials to call for better communication between Sinclair and local emergency response workers.

A fire in March temporarily slowed production at the refinery, and a separate equipment malfunction in May resulted in the release of a toxic gas that included a mixture of sulfur dioxide and hydrogen sulfide. No one was hurt in any of the incidents.

Company officials and DEQ inspectors worked last month to locate and neutralize the source of odors coming from the refinery that had prompted complaints from nearby residents. A storage tank and a separate cleanup site where decades-old contaminated soil was being disturbed were identified as likely causes.

At a meeting last month, Carbon County Commissioner Terry Weickum and county Assistant Fire Chief Larry Trapp asked refinery representatives to notify local emergency incident managers of serious incidents, citing poor communication by Sinclair following recent events.

Company representatives did not respond to messages left seeking more information.

The Associated press contributed to this report.