D.C. United officials said yesterday that they believe the stabbing of a soccer fan in the stands of RFK Stadium on Sunday was an unfortunate but "isolated" incident that does not require any heightened security measures for this weekend's home game against the Columbus Crew.

Sergio Senteno, 27, of Arlington, remained in stable condition yesterday at D.C. General Hospital after surgery for stab wounds to his lower back and abdomen.

"It was such an isolated incident," said D.C. United's president and general manager, Kevin Payne. "Generally, there were few problems. It's just an unfortunate thing. I don't know how you prevent something like that short of full body searches."

No arrests had been made by late yesterday. Police declined to discuss a possible motive for the stabbing, including whether the incident grew out of a soccer rivalry between Senteno and his assailant.

The stabbing occurred about 4:30 p.m. Sunday, police said, in the stands behind the northwest-end goal. This is a section of RFK where Salvadoran soccer fans were seated, waving their country's flag and cheering former United star Raul Diaz Arce, a Salvadoran, who now plays for the Tampa Bay Mutiny. The Salvadoran fans also booed United stars Marco Etcheverry and Jaime Moreno, who are Bolivian.

Rick Lawes, a spokesman for D.C. United, said fans in that area cheered Diaz Arce when he was near the ball and booed Etcheverry and Moreno when they were near the ball. But he said team officials do not believe the stabbing was the result of extreme partisanship among fans.

"We do not believe it was that way," Lawes said. "This was not one guy wearing blue and white [the colors of the Salvadoran flag] and one guy wearing a yellow and green shirt [the colors of the Bolivian flag]. It appeared to be nothing more than a random act of violence."

Lawes said that a knife was recovered but that it was not clear whether it was the weapon used in the stabbing.

During a previous appearance by Diaz Arce at RFK in April, when he played for the San Jose Clash, some of his fans scuffled with United fans in the stands and parking lots. As a result, stadium officials beefed up security for Sunday's game, adding hundreds of security officers and other workers, including at least 50 D.C. police officers.

Officer Kervin Johnson, a spokesman for the D.C. police, said officers still are looking for witnesses.

Fifth District detectives "could get very little" information on Sunday, Johnson said.

Major League Soccer Commissioner Don Garber, who attended Sunday's game and was named to his post just last week, called the stabbing "obviously a very unfortunate situation."

"It was one of the terrible things that can take place at any public event," he said. "It was an isolated incident and dealt with quickly." He said the league needs to be prepared "for these type of things," but he said there are no plans to increase security at stadiums.

Staff writer Steven Goff contributed to this report.