Two of the top five contenders for chief of the trouble-plagued Alexandria Police Department abruptly withdrew from consideration during the weekend, forcing City Manager Vola Lawson to scrap months of preliminary screening and start a new search.

Lawson said yesterday that even though three of the five finalists remain available for the chief's job, she does not believe that the city has "a broad enough pool of applicants" to choose from. She plans to advertise nationally for additional candidates, a task that will delay filling the job by at least two months until Feb. 1.

The withdrawals marked a serious setback for Lawson, who has had difficulty finding a replacement for former Police Chief Charles T. Strobel. He stepped down last month after controversies, criticism and an internal investigation.

When the vacancy was first advertised this summer, city officials were disappointed by the number of applications they received and ordered that it be advertised again.

Lawson said yesterday that she will loosen the requirements for the job when it is advertised for the third time. She had been considering only candidates who have worked as police chiefs in cities of at least 75,000 people. Now, she said, she will accept applications from chiefs and deputy chiefs.

Highly publicized conflicts between police officials and City Hall, along with problems within the department, have appeared to discourage some well-qualified applicants, even though the proposed salary is similar to that of police chiefs in other local jurisdictions. The new chief will be paid between $56,000 and $62,000 a year.

Strobel stepped down after an internal investigation cited "significant failure of top management in the Police Department." In 1985, Strobel was the target of a grand jury investigation that cleared him of any wrongdoing but forced him to take a lengthy leave of absence and appeared to undercut his authority.

Lawson said yesterday that she believes the department's problems have not jeopardized the search for Strobel's successor. "We have many fine people in the Police Department, and we have had expressions of interest from many qualified candidates," she said. "We just don't feel it would be wise to make the final selection from so narrow a field."

Lawson declined to identify the two finalists who pulled out. But she said that one is a lawyer who had decided to join a law firm in the city where he had been police chief. The other, she said, withdrew for "personal reasons."

According to city officials who asked not to be identified, two of the remaining three finalists were Alexandria's acting police chief, Arlen Justice, and former U.S. Capitol Police chief James Carvino.

Carvino, 53, of Oakton, resigned from the Capitol Police in June after one of his management decisions was questioned. He ordered members of his staff to produce a videotape while on duty and later gave it to a secretary as a retirement gift. Carvino is a former chief of police in Racine, Wis.

Justice has served for more than 20 years in the Alexandria Police Department, and before Strobel's departure he held the rank of deputy chief.

Although Carvino and Justice will continue to be eligible for the chief's job, they will not necessarily be among the finalists after new applications are received, Lawson said.

Justice was the only finalist from Alexandria. Two other city officials -- Deputy Police Chief for Administrative Services John Streeter and undersheriff Richard Ruscak -- were among the original 28 applicants, but Streeter withdrew his name and Ruscak did not meet the requirements, officials said.

There is evidence that many rank-and-file police officers would prefer that the new chief come from outside the department, a situation that one city official called "highly unusual."

Officers have complained privately about favoritism among senior police administrators and a lack of affirmative action programs. About 10 percent of the city's police officers are minorities, and 10 percent are female.

In a poll taken in August by the Alexandria Police Association, 117 officers said the department would be better served by a new chief from outside the city, association President J. Barry Shiftic said. Thirty-one members disagreed or said they had no opinion.

Shiftic said that written comments by officers during the poll, the results of which were conveyed to Lawson, indicated that they were not so much rejecting Justice as expressing their sentiment that only a newcomer can lift morale and make needed changes in the department.

"Obviously, anyone who comes in will have a honeymoon period, and they think that during that time some things might be accomplished," Shiftic said.

The selection process is being managed by Fairfax consultant Terry Eisenberg of Personnel Performance Inc., who will help select finalists from the new round of applications.