Alexandria police began an intensive investigation yesterday into the deaths of three young women and the disappearance of a fourth in the same crowded neighborhood of suburban apartment buildings along I-95 in the Landmark section of Alexandria.

All four women are presumed by the police to have been murdered. All four lived in the Landmark neighborhood, were under 35 years of age and were believed to be unmarried or separated.

The three bodies found so far - one last August, one last week and one Thursday - were fully clothed lying in wooded areas within less than a mile of each other.

Many residents of the area were apprehensive and frightened yesterday as police squad cars raced here and there on the crowded suburban roads and as teams of searchers, some of them with dogs, combed the lush woods and streambeds that lie among the buildings.

Young married couples and singles, both black and white, seem to be the predominant kind of tenants of this neighborhood of recently built high-rise and garden apartments straddling the busy I-95 highway a mile and a half inside the Capital Beltway on the west end of Alexandria.

Jeanette M. McClelland, a 24-year-old proofreader in a printing firm and known as a sensitive, quiet woman, lived in a five-story apartment building at 5445 N. Morgan St. - just 100 yards from the noise of traffic on I-95. Last Thursday afternoon she was found, stabbed to death in the chest in a culvert under the highway just through the woods and down a steep path from her home.

Jeanette McClelland had recently told her father, Robert D. McClelland, that last month, as she stepped out of the elevator in her Holmes Run Park apartment building, she "saw a man with a knife. He mumbled something, brushed past her, and Jeanette ran to her apartment."

Gladys R. Bradley, 27, a distribution clerk in the D.C. Post Office, lived in a similar building in the same Holmes Run Park apartment complex at 5420 N. Morgan - a building about halfway between McClelland's building and I-9. Bradley had been found apparently drowned in a stream about a mile away near yet another apartment complex last Saturday at 6:15 p.m.

Bradley was not visibly injured, police said, but showed signs of having drowned, according to a medical examiner's resort. Police said they are proceeding as if she were murdered.

McClelland's car was found parked near the same apartment complex where Bradley's body has been found, police said. This would place McClelland's car about a mile from the spot where her body was found.

Aletha Byrd, 34, who worked in the employment section of Woodward and Lothrop at Tysons Corner, lived in the same apartment building as McClelland. A friend reported her missing on April 10, and last Thursday police found her apparently abandoned car in an apartment building parking lot just on the other side of I-95 from where she lived.

Anyone who walked through the culvert - a huge concrete pipe - where McClelland's body was found would be within a few yards of the parking lot where the Byrd car was found.

The culvert is isolated and surrounded by woods and is known as a beer-drinking area and local lovers lane, area residents said. Obscene pictures and words are painted inside it. The trickle of the stream over rocks muffles the noise of the automobiles racing by just overhead.

Police searching for Byrd's body yesterday moved farther and farther down Holmes Creek toward the Potomac, where police boats also searched for her body.

Aura Marina Gabor, 24, born in Guatemala, lived in another apartment complex only a few hundred yards southwest of Holmes Run Park. In early August of last year, she was found strangled and lying in a creek next to I-95.

While police are reluctant so far to connect this long-ago murder directly with the others, they have left open the possibility of a connection and have actively reopened the case.

Bradley's car was found only a few blocks from the Gabor death site and located on the same street - North Armistead - where Gabor lived.

Alexandria police Capt. Clyde Scott, who is in charge of the investigation, said yesterday he had no strong leads and no suspects.

Despite the apparent connections among the cases, Scott said he is remaining open-minded as to the extent of connections among the deaths and disappearance and as to whether one suspect or many suspects will be sought.

Scott said that all 21 of his detectives are working on the cases and that large numbers of additional police officers are conducting the search for the missing woman.

He said other police departments in the area are helping and that the FBI has provided some technical assistance, although is now otherwise active in the cases.

Scott said that an autopsy yesterday disclosed that McClelland had died from stab wounds in the chest. She was fully dressed and wearing a pair of jeans when found, Scott said.

Gladys Bradley also had been found fully clothed and wearing a raincoat, Scott said. Scott said neither woman appeared to have been sexually molested, but that conclusive lab tests to determine this have yet to be completed.

When asked, Scott said he could see no "ritual" or execution-style aspect to any of the deaths. The Gabor woman had also been found clothed, police said.

Scott said neither McClelland nor Bradley had purses with them, but that this was no enough information to reach a conclustion as to whether robbery might be involved.

Scott said he did not believe there are any connection between the cases he is investigating and the body of the 22-year-old unidentified female found apparently shot to death on Indian Head Highway in Maryland, though this death site is only a 15-minute drive by superhighway from the Alexandria scene.

Scott said he believed this body had been found nude, and that this and other known facts about the case made it seems not to fit the pattern of the four cases he is investigating.

Scott said the McClelland case is "definitely a homocide" and that in the Bradley case he is procedding "as if it were a homicide."

"We've dropped everything and set up a research team to search old records," said Scott. He said the team is searching for any possible connection - "anything related to prowlers, peeping toms. We're doing a complete search trying to pick up possibilities."

He said his researchers are also going over records of releases from prisons and mental institutions looking for anything that might be useful.

"It's going to be an elimination process," he said of the investigation as a whole.

The Holmes Run Park apartment complex consists of five mid-rise buildings and 22 garden apartment buildings where rents start at about $215 for a one-bedroom apartment.

Residents interviewed yesterday at 5445 and 5420 N. Morgan said the complex is plagued with frequent outbreaks of petty vandalism, noisy neighbors and violent fights.

A couple who live on the fifth floor at 5445 N. Morgan - the same floor as Byrd's apartment - said police indicated to them that they were working on the assumption that the women might have been approached in the apartment complex's parking lot.

"The guy probably met them in the parking lot," said the resident, who asked not to be named. "The abduction, where they leave the car, and where the body is found are all in the same general area."

"I'm not going to run, but my wife is very scared," said Michael Creel, who lives on the same floor that McClelland did. "But we just signed a lease and we're kind of stuck here."

A woman who lived in an apartment near Byrd's said she remembered the missing woman from their shared elevator ride and said she also remembered the noisy quarrels that frequently appeared to be coming from Byrd's apartment.

Byrd was "pretty much of a private person," said his woman, who asked that her name not be used.

Lugene White, who lives at 5445 N. Morgan, said, "I just moved in here last Saturday. I thought I was moving into a better neighborhood. You just can't win, can you?"

Spokesmen for Dreyfuss Bros. Inc., which manages the Holmes Run Park complex, said they had no comment about the cases or about some residents' charges that there is a lack of security at the complex.

Some residents spoke of the widely publicized execution-style murders that occurred at a nearby Roy Rogers restaurant, early last year, "within spitting distance," as one resident said.

James Leroy Breeden, a 39-year-old unemployed mechanic, was convicted early this year of slaying four persons in the freezer of the restaurant by systematically shooting them as they lay on the floor.

Breeden, who is in prison, formerly resided on N. Armistead near the place where the Gabor body was found and also near where the Bradley car was found.