Ted Stevens and eight others on board plane that crashed in Alaska

A plane carrying nine people crashed amid southwest Alaska's remote mountains and lakes, killing five people on board, authorities said Tuesday. Former Sen. Ted Stevens and ex-NASA Administrator Sean O'Keefe were believed to be aboard, but it was unclear if they were among the dead.

Reports from officials in Alaska were that nine people were aboard the aircraft and that "it appears that there are five fatalities," NTSB spokesman Ted Lopatkiewicz told The Associated Press in Washington.

A U.S. government official told The Associated Press that Alaska authorities have been told that the 86-year-old Stevens, a former longtime Republican senator, was on the plane. The official, who spoke on grounds of anonymity, says Stevens' condition is unknown.

The federal official declined to be publicly identified because the crash response and investigation are under way.

Stevens was one of two survivors in a 1978 plane crash at Anchorage International Airport that killed his wife, Ann, and several others.

Defense contractor EADS North America said Tuesday morning that O'Keefe, the CEO of the U.S.-based division of the European company, was a passenger on the small plane. The company said it had no further information about O'Keefe's status.

Alaska National Guard spokesman Maj. Guy Hayes said the Guard was called to the area about 20 miles north of Dillingham at about 7 p.m. Monday after a passing aircraft saw the downed plane. But severe weather has hampered search and rescue efforts.

Hayes said five people were on scene early Tuesday helping the crash victims. It was unclear how they reached the site.

A second U.S. government official in Washington said Tuesday that the National Guard in Alaska reported a private medical team was dropped near the crash site by commercial helicopter Tuesday morning. Four of nine people aboard the plane survived, the official said.

Coast Guard Petty Officer David Mosley said the agency has a plane flying over the crash scene, scouting it to make sure it's safe for helicopters to come into the area with pararescuers.

The National Weather Service reported rain and fog at Dillingham, with low clouds and limited visibility early Tuesday.

Conditions ranged from visibility of about 10 miles reported at Dillingham shortly before 7 p.m. Monday to 3 miles, with rain and fog, reported about an hour later, according to the agency.

Steven and O'Keefe are longtime fishing buddies and the former senator had been planning a fishing trip near Dillingham, longtime friend William Canfield said. The flight in and out of Dillingham is an often perilous trip through the mountains even in good weather, Canfield said.

Stevens, a moderate Republican, was appointed to the Senate in 1968 and served longer than any other Republican in history.

He remarried several years after the 1978 crash — he and his second wife, Catherine, have a daughter, Lily.

Over the years, Stevens directed billions of dollars to Alaska. But one of his projects — infamously known as the "Bridge to Nowhere" — became a symbol of pork-barrel spending in Congress and a target of taxpayer groups who challenged a $450 million appropriation for bridge construction in Ketchikan.

Stevens' standing in Alaska was toppled by corruption allegations and a federal trial in 2008. He was convicted of all seven counts — and narrowly lost his Senate seat to Democrat Mark Begich in the election the following week.

But five months after the election, Attorney General Eric Holder sought to dismiss the indictment against Stevens and not proceed with a new trial because of prosecutorial misconduct by federal prosecutors.

Stevens' family thanked those trying to reach the site of a plane crash in southwest Alaska in a statement released Tuesday morning by a former Stevens chief of staff.

Lopatkiewicz said the NTSB is sending a team to the crash site.

In Washington, a Federal Aviation Administration spokesman said the aircraft is a DeHavilland DHC-3T registered to Anchorage-based General Communication Corp.

Dillingham is located in northern Bristol Bay, about 325 miles southwest of Anchorage.