VERNAL, Utah (AP) - A leak of drilling fluids from a natural gas well that spread toward the White River and a strange foam that appeared on the Green River have state environmental officials investigating pollution found near the eastern Utah rivers.

Enduring Resources, a Colorado-based energy exploration company, reported a leak from a natural gas well reserve pit to the Bureau of Land Management Thursday.

Although the lined reserve pit is located on property managed by the Utah School and Institutional Trust Lands Administration, about 1,200 gallons of drilling fluid had leaked from the reserve pit across BLM-managed land in Atchee Wash, about 40 miles south of Vernal.

When the leak was discovered crews immediately constructed two berms in an attempt to contain the spill, said Alex B. Campbell, vice president for Enduring Resources. A vacuum truck was used to remove the fluid from the berms and empty the reserve pit and the fluid was stopped about one mile away from the White River, Campbell said.

The fluid stopped a few hundred feet from the river, according to a Friday release issued by the BLM.

The BLM said it is investigating the leak and water samples have been taken from the leaking pit, immediately outside the pit, where the fluid was stopped and at the White river.

The leaking reserve pit is a fresh/water mud system that could contain barite, a component of drilling fluid used to add weight and minimize fluid loss into underground formations.

The White River enters northeastern Utah from Colorado. It empties into the Green River, which was the focus of an investigation by the state Division of Water Quality earlier this week after the agency received reports of foul-smelling foam on the river.

The foamy substance found floating in the Sand Wash area of the Green River was determined not to be harmful, according to test results. But the testing was not done until eight days after the foam was first reported.

"We don't know if it was man-caused or a naturally occurring phenomenon," Utah Division of Water Quality director Walt Baker said.

A breakdown in communication between state agencies kept DWQ out of the loop between the first report of the foam on March 12 until Monday, which made collecting samples and testing less effective, he said.

Baker said there are foaming agents in some of the drilling fluids used by energy exploration companies in the area. While there is no evidence suggesting drilling fluid was the cause of the foaming it has not been ruled out, Baker said.

It's also common for foaming to occur on the river in spring when increased runoff transports fatty acids from decomposing plants, leaves and algae into streams and rivers, he said.

"Because we weren't able to be there on site, see (the foaming), capture it and test it in the field under a microscope, we may never know what caused it," he said.