An Advanced Life Support ambulance that was summoned Tuesday to treat an injured police officer took so long to reach the scene that a basic ambulance was eventually sent, according to accounts from the fire department and the firefighters union.

The incident raised new questions about the ability of the fire department to provide medical services in a timely manner.

The incident began shortly before 4 p.m. with a call about an injury to a police officer at 13th and Monroe Streets NE. The officer’s injuries were ultimately described as not life threatening.

From phone logs that union members provided, it appeared that a fire truck was first to reach the scene. A paramedic ambulance was summoned shortly afterward. That vehicle was apparently sent at 3:55 p.m.

After it had not reached the scene for some time, a basic life-support ambulance was sent at 4:06 p..m., arriving two minutes later. The officer was taken to a hospital.

The Advanced Life Support unit arrived at the scene after the arrival of the basic life support unit, said Fire Department spokesman Timothy J. Wilson.

Wilson said the ALS unit had been about four miles away when dispatched. By one account, it was at 12th Street and Constitution Avenue NW, and would have required 15 minutes or more to reach the scene under prevailing traffic conditions.

Wilson said that half of the department’s advanced ambulances were downgraded to basic units Tuesday for the period between 7 a.m. to 7 p.m. Such downgrades often occur when personnel unexpectedly do not show up for their shifts.

Full ALS staffing is less difficult when more staff members arrive for their shifts, or others volunteer to fill in, Wilson said.

Union leader Edward C. Smith, who has been critical of the department’s leadership, said the incident was another demonstration of its failings.

“Time and time again, we’ve shown we can’t deliver service,” he said.

Irrespective of who is injured, he said, “everybody deserves better.”