JUNEAU, Alaska — A plane believed to be carrying eight people, including former US Senator Ted Stevens, crashed in southwest Alaska and rescue crews were trying to reach the wreckage early Tuesday, authorities said.

Alaska National Guard spokesman Maj. Guy Hayes said there were possible fatalities. Five people were on scene early Tuesday helping the crash victims, he said. It was unclear how they reached the site.

A US government official told The Associated Press that Alaska authorities have been told the former longtime Republican senator is among several passengers 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.

Hayes said the Guard was called to the area about 20 miles (30 kilometers) 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 he was told by Alaska State Troopers that there were "eight or nine" people on board, though a spokeswoman for the troopers, Megan Peters, refused to comment.

She said all the agency could say for sure is that a plane went down and crews were "aggressively" trying to reach the crash site but having difficulty doing so. As of 4 a.m. Tuesday, she said she still hadn't received word that crews had reached the site.

"I can't go beyond, 'We're responding to a plane crash,'" she said.

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.

Stevens, a moderate Republican, was appointed to the Senate in 1968 and served longer than any other Republican in history. He directed billions of dollars to Alaska over the years.

A National Transportation Safety Board investigative team has been dispatched from Washington, D.C., to the crash site and was expected on the ground Tuesday morning.

In Washington, a Federal Aviation Administration spokesman said the aircraft is a DeHavilland DH3T registered to Anchorage-based GCI Communication Corp.

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