ALDERSON, W.Va. (AP) _ Federal agents put out a nationwide alert as 100 officers trudged over the West Virginia hills Thursday hunting prison escapee Lynette ''Squeaky'' Fromme, the Manson follower who tried to kill President Ford.

Fromme, 39, was discovered missing from her room at the Alderson Federal Prison for Women during a routine check about 9:30 p.m. Wednesday, said Warden Ron Burkhart. Other inmates reported last seeing Fromme about 10 minutes before the 9 p.m. check began, he said.

The former disciple of mass murderer Charles Manson was serving a life term for attempting to shoot Ford in Sacramento, Calif., in 1975. She had been eligible for parole consideration since September 1985, but waived her right to a parole hearing and elected to remain in prison, Burkhart said.

Numerous sightings of a woman matching the red-haired fugitive's description have been reported by area residents, but Burkhart said none of the tips have panned out. Officials said they weren't sure what she was wearing at the time of her escape; inmates are not required to wear prison uniforms.

Jesse South, chief deputy U.S. marshal, said authorities in all 50 states have been notified of Fromme's escape. The Secret Service and U.S. marshals were interviewing people with whom she recently had contact, said Burkhart.

More than 100 agents accompanied by dogs scoured 10 square miles of rugged hills and woods surrounding the prison in southeastern West Virginia. The search would continue into the night, officials said. At the prison, officials made a second check of the prison's 69 buildings.

''Sooner or later I'm confident we'll get her back,'' Burkhart said. ''In the world there aren't many places for a Lynette Fromme to go.''

''We're going to stick with it as long as there's hope she's still in the mountains,'' he said. He said 10 to 14 two-man patrols would continue searching on Christmas Day.

''I'm operating on the assumption she's still around here - but that's strictly an assumption,'' he said.

The weather was described as clear, with a light wind. Temperatures ranged from a morning low in the 30s to afternoon readings in the 50s.

Burkhart said prison officials had no clue how she escaped or why, but speculated she either scaled or slid under an 8-foot fence, some of which is topped with coiled barbed wire, surrounding the complex.

''There's no physical evidence of how she got out or where she went,'' he said.

Ford declined comment on the escape, according to his spokeswoman in Palm Springs, Calif.

Ford was unharmed when a Secret Service agent grabbed a semi-automatic .45- caliber pistol aimed at him by Fromme on Sept. 5, 1975.

In San Francisco 17 days later, Ford escaped injury when Sara Jane Moore, a 45-year-old political activist, fired a revolver at him. She eventually pleaded guilty and received a life sentence.

In 1979, Moore also escaped from the Alderson prison, but was recaptured hours later about 25 miles away. She is now in a federal prison in Pleasanton, Calif.

In a telephone interview Thursday, Moore said escaping from the prison was easy but staying free was difficult. ''On foot, you have almost no chance. You almost have to have a car,'' Moore said.

''Everybody knows everybody and they know if you belong. If you're not from there, you stand out like a sore thumb,'' she said.

Fromme was the first person sentenced under a special federal law covering assaults on presidents, a statute enacted after the 1963 assassination of President John F. Kennedy.

She spent 2 1/2 years at the West Virginia prison and was moved to Pleasanton in 1978 after prison officials said she had become a ''model inmate.'' But she was sent back to Alderson in 1979 for striking another inmate with a hammer.

Fromme, assigned to housekeeping duties in one of Alderson's medium- to high-security cottages, had behaved since then, Burkhart said.

''It wasn't until last night that she presented a problem for us,'' he said Thursday.

There have been 15 escapes from Alderson in the past two years.

Fromme has corresponded with Manson and several other of his followers, said Burkhart.

Manson is serving a life sentence in San Quentin prison in California for the 1969 murders of actress Sharon Tate and eight other people in two consecutive nights.

Sandra Good, another Manson follower and Fromme's one-time roommate, also was housed at the Alderson prison. She was paroled Dec. 2, 1985, and moved to Vermont. She had been convicted of making threatening telephone calls.

Neither Fromme nor Good was charged in the Tate killings.

Author Mary Neiswender in Los Angeles, who has closely followed both Moore and Fromme, described Fromme as ''the cornerstone'' in keeping Manson family members in communication with each other.

''Squeaky was probably one of the most devoted members of the family and did the most to keep it together when it started falling apart,'' Neiswender said.

Stephen Kay, one of the California prosecutors in the Manson murder case, who has followed Fromme's case, said she waived her parole hearing in 1985 and elected to stay in prison because ''she wasn't going to get it anyway.''

''And asking for parole, that would have been admitting something, and Squeaky wasn't going to cooperate with the system,'' Kay said. ''She'd rather escape.''

Robert Snow, a spokesman for the Secret Service in Washington, D.C., refused to say what, if any, security precautions are being taken to protect Ford following the escape.

''We're taking what we feel are appropriate steps to keep things secure,'' Snow said. ''We're not going to give any specifics on what's been done.''