Alexandria officials said yesterday that they are investigating whether three city police officers acted properly when they entered the back yard of City Council member Donald C. Casey and administered breath tests to two of his teen-aged children, who were having an argument.

"There is absolutely no question that using those tests was was improper," said Casey, who filed a complaint about the Memorial Day incident. "This is harassment."

Casey, a patent lawyer who has been an outspoken critic of the police department, said that city officers rarely use the small portable device to check for alcohol use on other than suspected drunk drivers.

"You tell me the last time an Alcosensor test was used in Alexandria on private property," he challenged.

Police officials said that the actions were not illegal, but agreed that Alcosensor tests are used almost exclusively to help determine the sobriety of drivers.

Acting City Manager Vola Lawson refused to comment on the complaint, but a spokeswoman said that no disciplinary measures would be recommended until the conclusion of the investigation.

Casey said, however, he understood that Lawson had agreed to transfer Guy Bishop, one of the officers involved, and discipline the others.

Casey, who was defeated in the city's May 7 election, said police went to his home early on May 27 after an anonymous caller reported a disturbance.

Casey and his wife were out of town at the time. His children, aged 17 and 19, where quarreling when the police arrived, according to sources familiar with the investigation.

The incident comes at a time when the Alexandria Public Safety Department has been hit by morale problems and widespead unhappiness over the city's decision to reduce some of its benefits.

It also comes only a month after Lawson ordered sweeping changes in the department as a result of a separate incident, in which several police officers, including Bishop, were disciplined for failing to respond properly to an emergency call from an 89-year-old woman who had been robbed and sexually abused.

City officials, who asked not to be named, said that the police and city officials have agreed to seal the records of the investigation. No charges will be filed in the case, according to the officials.

Casey said that he believed the internal police investigation had been handled well, but that by detaining his children for almost 30 minutes while the third officer brought the machine for the breath test, the police had invaded their privacy and harassed them.

"I think it's pretty clear there was not a random reason for this," said Casey, who has had two meetings with Lawson and John V. Streeter, the deputy director of Public Safety who is overseeing the investigation.

Streeter would not discuss particulars of the investigation, saying that he "assured the city manager that I will not talk about this matter." He added that he was not sure when the investigation would be concluded.

Police officials said that there is no policy that prohibits police from using Alcosensors on private property.

"It is a question of judgment," said one officer.