A 26-year-old Manassas man died Sunday afternoon at Prince William Hospital after he collapsed while playing basketball and did not receive advanced life support treatment for 17 minutes, according to county and hospital records.

In a similar incident the same day and only a few miles away, a 68-year-old woman who suffered a heart attack did not receive advanced life support until she arrived at the same hospital 23 minutes later. She was listed in critical condition yesterday, hospital officials said.

The incidents are the latest to draw attention to Prince William County's volunteer-dominated fire and rescue service, which came under attack last week when a Dale City man died of a heart attack after waiting 32 minutes for an ambulance.

On Tuesday the Board of County Supervisors moved to revamp parts of the service. However, the changes, some of which take affect next week, will not alter coverage on weekends -- when volunteers are the only ones on duty, and when the latest two incidents occurred. Critics have complained that advanced life support treatment is not consistently available when the county's paid personnel are not on duty.

In one of Sunday's incidents, Wayne Thomas of the 800 block of Brigade Court in Manassas collapsed around 3:45 p.m. while playing basketball at Stonewall Middle School. Two rescue vehicles arrived within minutes, according to fire and rescue service records, but neither volunteer team was trained to administer lifesaving drugs or to operate the vehicles' sophisticated equipment, such as defibrillators and heart monitors.

Thomas was given cardiopulmonary resuscitation and taken to nearby Prince William Hospital, where the advanced treatment was begun, 17 minutes after the call for help went out.

He was pronounced dead about an hour later, hospital officials said. An autopsy indicated he died of a heart attack.

In the other incident, volunteer personnel responded within minutes to a call for help for Sadie Martin of the 8000 block of Ashland Avenue but again could not provide advanced treatment, according to fire and rescue service records. Martin, who also suffered a heart attack, arrived at Prince William Hospital 23 minutes after the call was placed.

Northern Virginia medical examiner Frances Field said yesterday that it is not possible to say whether advanced life support would have saved Thomas' life. Medical groups say that a patient's survival chances are increased if CPR and advanced life support measures are administered quickly.

Prince William County Executive Robert S. Noe Jr., responding yesterday to Thomas' death, said: "I think this incident points to the not-as-well recognized part of our problem. Most people assume that an ambulance responds with state-of-the-art capability. That is not so. We have a problem with both response time and training."

Among its actions Tuesday, the board of supervisors decided to stagger the shifts of paid fire and rescue personnel, starting next week, to provide advanced life support capability during what critics have called "windows of vulnerability" -- between 5 and 7 during the morning and evening on weekdays. Paid personnel work 7 a.m. to 5 p.m., with weekends and holidays off.

The county's fire and rescue service is run by proudly independent volunteers, who have proven resistant to interference on the part of county officials.

Only a small number of volunteers are trained to provide advanced life support, according to Dr. Rodolfo Lopez, one of the county's two medical directors.

According to a study he conducted last year, Lopez said, volunteers were able to provide advanced treatment 30 percent of the time they had responsibility for doing so; paid personnel were able to do so 100 percent of the time they were responsible for treatment.