ANCHORAGE, Alaska — Natural gas for at least 10 days has leaked from an underwater natural gas pipeline in Alaska’s Cook Inlet and floating ice has prevented divers from reaching the site.

The gas is bubbling from an 8-inch pipeline in 80 feet of water about four miles off shore. The pipeline belonging to Hilcorp Alaska, LLC, moves processed natural gas from shore to four drilling platforms in the inlet.

The Alaska Department of Environmental Conservation is investigating the leak. In an email response to questions, spokeswoman Candice Bressler said the agency is assessing public health and environmental risks.

“We believe the risk to public health and safety is small,” the agency said. “Environmental risk is less easy to quantify since a monitoring and assessment program is not yet in place.”

The federal Pipeline and Hazardous Materials Safety Administration also is investigating.

The Coast Guard warned mariners to stay at least 1,000 feet from the bubbling gas. Another federal agency expressed concern over possible adverse effects on marine mammals.

“Our greatest concern is for endangered Cook Inlet beluga whales and impacts to their critical habitat,” said Julie Speegle, spokeswoman for the fisheries section of the National Oceanic and Atmospheric Administration. The natural gas discharge is within the winter foraging area for the whales, she said.