A four-alarm fire that destroyed a 40-unit Prince George's County apartment building and left 140 homeless early yesterday allegedly was set by a 25-year-old construction worker who neighbors said was seeking revenge against his 18-year-old girlfriend.

"I saw him out there after the firemen came and he was saying, 'I lit the fire and I don't really give a damn,'" said a witness, referring to William Mark Wrubleski, who has been charged with arson in the blaze.

Wrubleski, a resident of the Bryant Woods apartment complex in the 5300 block of 85th Avenue in New Carrollton where the fire occurred, is being held in the county detention center in Upper Marlboro in lieu of $200,000 bond. If convicted, he could face up to 30 years in prison.

He was arrested on the basis of information obtained from witnesses at the fire scene, investigators said.

The fire was the fourth major blaze in Prince George's County in the past five days, and the second at the Bryant Woods complex. Fire officials reported no evidence linking Wrubleski with the first blaze at the complex on Friday, which left an estimated 60 persons homeless.

More than 200 firefighters and 31 pieces of equipment responded yesterday to the alarms sounded at the three-story brick garden apartments before the fire was brought under control at 1:30 a.m. No serious injuries were reported. Damage was estimated at $800,000, and officials of the American Red Cross said most of those who lost their possessions carried no insurance against fire.

"I guess they're all just going to start over again," said Rudy Watkins, a Red Cross spokesman.

According to neighbors, Wrubleski repeatedly had threatened to burn the building down if his girlfriend, Linda Halbritter, moved out of the apartment they had shared for a year. The two had argued Saturday evening about Linda's plans to attend a birthday party for a childhood friend, her mother said.

"She had been trying to leave him for a while," said a distraught Barbara Halbritter, fumbling with her bathrobe as she sat in the living room of her Bryant Woods apartment, several hundred yards from the site of the blaze. h

Mrs. Halbritter said she attended the party with her daughter, only to find that Wrubleski had followed them and was standing sullenly outside the door. As the party was breaking up, she said, she drove Wrubleski back to his apartment. A few minutes later, fire trucks started to arrive.

The woman said her daughter was with her in her apartment when they heard the commotion outside. Almost at once, Linda said she thought that Mark had "set the place on fire," Mrs. Halbritter said. "She didn't even go to the window to look."

Linda Frank, who lived in Wrubleski's apartment building and said she had known him for eight years, said she heard Wrubleski in the parking lot as the fire raged, telling friends, "It started in my apartment and I started it and I don't care."

Frank, who lost all of her belongings in the blaze, said Wrubleski "just didn't care about anything or himself, really."

Wrubleski's estranged wife Vicky yesterday expressed shock over the arrest, and said former football player for DuVal Senior High School in Lanham was not capable of arson.

"He's a very good person -- he's not weird," she said, adding that family members suspected that blame for the fire was being pinned on her husband by fire officials looking for an easy solution to the crime. "He's never been a violent person, and I just don't believe he would ever do anything like that."

She said Wrubleski, who has worked five years for a local concrete construction firm, had "never threatened to burn a house down or . . . any of that," in the three years they were together.

Wrubleski's cousin, Scott Wright, a volunteer in the Riverdale Heights Volunteer Fire Department who had been among the first firefighters to reach the scene Sunday morning, said two malfunctioning water hydrants delayed firefighting efforts by approximately 15 minutes. He said the fire possibly could have been limited to one apartment if the hydrants had been working.

But Prince George's fire chief Jim Estepp said yesterday such difficulties were caused by low water pressure and were not unusual.

"You're talking about many, many units (drawing on the water system)," Estepp said. "No system is designed to handle that much fire."

Wright, who said he had not slept for two days, said county firefighters felt as theough they were in the "eye of a hurricane" after losing one comrade in a two-alarm blaze last Wednesday and enduring four major fires in five days.

"I can't recall anything like it in 20 years," said Estepp. "It's been a terrible week. Everybody's maxed out."

For one Bryant Woods resident, Denise Logan, 19, who had come home from a party early in the morning to see her apartment ablaze, there was good news yesterday.

Her tiny black-and-white dog Panda, who had been trapped in the apartment when the fire began, was brought out of the debris covered with soot by firefighters yesterday afternoon.

"I was really scared for him," said Logan, cradling Panda in her arms. "I'm just glad he's okay." She said the dog had probably survived by burrowing into a pile of wet clothing.

By last night, all 140 residents, many of whom lost all their clothing and belongings, had found temporary lodging with their friends or relatives, according to Red Cross spokesman Mark McLachlan.