By Yereth Rosen

ANCHORAGE, Alaska (Reuters) - Investigators hunted for clues on Friday to determine who shot to death two members of the U.S. Coast Guard at a communications station on Alaska's Kodiak Island, federal officials said.

Agents are treating Thursday's killings, the first fatal shootings at a Coast Guard facility in Alaska in over a decade, as a double homicide, said Eric Gonzalez, an Anchorage-based special agent for the Federal Bureau of Investigations.

"No arrests have been made in connection with the shootings," Gonzalez said. "We are obviously trying to determine the person responsible for the murders."

The two victims worked at a communications station that is part of the Coast Guard's sprawling base in Kodiak, the main city on the large southwestern Alaska island of the same name.

Discovery of their bodies Thursday morning triggered a series of security measures at the base and in nearby Kodiak schools, including imposition of lockdowns in which base personnel and students were kept indoors as a precaution.

As of Friday, the lockdown of the Coast Guard installation had been lifted, Petty Officer Charly Hengen said. But the Coast Guard was asking its personnel, family members and Kodiak residents to be on alert and to report any suspicious behavior as the hunt for a suspect continued.

Hengen added that there was no evidence to suggest the deaths resulted from a murder-suicide. Identities of the victims were expected to be released later on Friday, she said.

The last instance of fatal gun violence at a Coast Guard facility in Alaska occurred in 2001, when the commander of a small, remote station in the Bering Sea was shot to death by a civilian.

The gunman in that case, angry that his civilian wife and the Coast Guard commander were having an affair, was convicted in 2003 of first-degree murder and other charges. At the time, officials said they believed the case marked the first murder of a Coast Guard member ever on Coast Guard property.

Kodiak, a city of about 6,300 people, is located 250 miles southwest of Anchorage.

The Coast Guard Base Kodiak, home to 1,000 active-duty personnel and hundreds of civilian employees, is the largest installation in the Coast Guard system, according to the Kodiak Chamber of Commerce and Kodiak Island Convention and Visitors Bureau.

The base is the center of operations for enforcement patrols and search-and-rescue missions in much of the North Pacific and in the Bering Sea, and conducts missions as far north as the Arctic Ocean.

(Editing by Steve Gorman, Cynthia Johnston and Philip Barbara)