FREDERICK, Md.

-- Two men wanted for questioning in the wave of deadly sniper attacks were arrested early today after they were found sleeping in their car at a Maryland rest stop, authorities said.

The arrests raised hopes of a conclusion to the intensive and often frustrating investigation of the shootings that have killed 10 people and critically wounded three others since Oct. 2 in the Washington, D.C., area.

The men taken into custody were not immediately charged in the sniper attacks, but authorities made clear the arrests were considered pivotal. The lead investigator described one of the suspects as ''armed and dangerous,'' and a newspaper report said the men were motivated by anti-American bias.

The arrests occurred hours after authorities descended on a home in Tacoma, Wash., believed to hold clues important to the investigation. They then issued a nationwide alert for the car, spotted by a motorist and an attendant at the rest stop.

The key break, authorities said, was a phone call to the sniper task force tip line suggesting investigators check out a liquor store robbery last month in Alabama in which two people were shot, one of them fatally.

The caller said to look at an incident in ''Montgomery,'' a law enforcement source told The Associated Press on condition of anonymity. Investigators checking the tip matched it with the Sept. 21 robbery in Montgomery, Ala., where, according to the source, they found a fingerprint from one of the men arrested today.

Montgomery Mayor Bobby Bright said the person who called the tip line apparently claimed responsibility for both the sniper shootings and the liquor store robbery.

Members of the sniper task force arrested the men without incident at 3:19 a.m. off I-70 in Frederick County, Md., about 50 miles northwest of the nation's capital, said Larry Scott, an agent for the federal Bureau of Alcohol, Tobacco and Firearms.

The men were arrested in a car that matched a description police gave at a midnight press briefing, said Maj. Greg Shipley, a spokesman for the Maryland State Police.

''I don't know what their reaction was,'' Shipley said. ''It wasn't an aggressive one.''

Charles Moose, the Montgomery County, Md., police chief who is leading the investigation, had said John Allen Muhammad, 42, was being sought for questioning in the slayings and called him ''armed and dangerous.'' Muhammad was said to be traveling with a juvenile, identified by a law enforcement source as 17-year-old John Lee Malvo.

The law enforcement source told the AP that police found a piece of paper at the scene of the Alabama shooting that bore Malvo's fingerprints. Police then traced Malvo to the Tacoma home, where he had been living with Muhammad, the source told the AP.

The relationship between the teen and Muhammad, who also goes by the name John Allen Williams, was not clear, but several newspapers reported that Malvo is Muhammad's stepson.

The law enforcement source told the AP that ''I'm confident that these are indeed the people'' sought in the killings.

''The evidence is all there and because of things we've received in the communications,'' the source said. ''It fits together with evidence they've collected in the last couple days.''

Several federal sources told The Seattle Times that Muhammad and Malvo may have been motivated by anti-American sentiments in the wake of the Sept. 11 attacks. Both were known to speak sympathetically about the men who hijacked jetliners over Washington, New York and Pennsylvania, the sources told the newspaper.

But neither man was believed to be associated with the al-Qaida terrorist network, the sources said.

The Times reported that Muhammad was stationed at Fort Lewis outside Tacoma in the 1980s, served in the Gulf War and was later stationed at Fort Ord, Calif. Malvo, who authorities said is a citizen of Jamaica, attended high school in Bellingham, Wash., last year.

Shipley said the men were being transported to Montgomery County, where the investigation is based.

The witnesses at the rest stop called police at 1 a.m. after they spotted the men sleeping inside one of the cars sought in the investigation -- a blue 1990 Chevrolet Caprice.

Moose had cautioned that it shouldn't be assumed Muhammad is involved in any of the shootings that have stricken the Washington area since Oct. 2.

On Wednesday, FBI agents spent hours at the Tacoma home, eventually carting away a tree stump from the yard and other potential evidence in a U-Haul truck.

Scott, the ATF spokesman, said the stump would be brought to the agency's lab in Rockville, Md., for ballistics testing. On background, law enforcement sources said they believed the stump might contain bullets or fragments.

Late Wednesday night, Moose held a media briefing where he issued his latest cryptic message in his ongoing dialogue with the sniper.

''You have indicated that you want us to do and say certain things. You've asked us to say, 'We have caught the sniper like a duck in a noose.' We understand that hearing us say this is important to you,'' Moose said.

He also expressed frustration at the failure to make contact despite the sniper's repeated attempts through ''notes, indirect messages and calls to other jurisdictions.'' He asked the sniper to call.

Several hours after the arrests, spokesmen at the Pentagon said they had no information and referred calls to the agencies handling the case. Defense officials had said last week that, at the investigators' request, the Army was searching its records of people trained as snipers for any former or current service member who might be involved in the shootings.

A Fort Lewis spokesman did not return a call for comment on whether Muhammad was stationed on the base.

Felix Strozier, who ran a karate school with Muhammad in 1997 and 1998, said Muhammad told him he had been in the Army but did not say where.

Pfc. Chris Waters, a Fort Lewis soldier who lives across the street from the Tacoma home, said he called police after hearing gunshots in the neighborhood nearly every day in January.

''It sounded like a high-powered rifle such as an M-16,'' he said. ''Never more than three shots at a time. Pow. Pow. Pow.''

Dean Resop, who lives a block away, said quite a few tenants had been in and out of the home.

''Makes you want to watch your neighbors closer,'' said Resop, who has lived in the area seven years.

FBI agents visited Bellingham High School, 90 miles north of Seattle, on Wednesday. Mayor Mark Asmundson told the Bellingham Herald the agents were apparently seeking information on a male teenager who once attended the school and an older man. He said both left the area about nine months ago.

Muhammad's ex-wife, Mildred, was being questioned by the FBI Wednesday, said Adele Moses, who identified herself as the woman's sister. She said Mildred was living with her in Clinton, Md., southeast of Washington.