District firefighters on Monday transported a critically ill infant to a hospital in a fire engine because an ambulance was too far away to respond in a timely manner, according to city officials.

A fire department spokesman said the firefighters were called because the child was not breathing. The infant was treated and released from a hospital and was at home.

Advance care paramedics aboard an engine were treating the infant within seven minutes, according to the department. Fire officials had initially said that the child was in cardiac arrest.

It was the second time in a week that a long response time prompted firefighters to take a patient to the hospital in an engine or put a patient in a fire truck. On Sept. 3, an infant from Southeast was transferred from a truck to an ambulance, and later died at a hospital.

Both cases are under investigation. In each instance, Gregory M. Dean, the chief of the fire and emergency medical services department, blamed the lag in an ambulance on call volume and people dialing 911 for minor issues, tying up critical care for others.

The District’s fire department has for months struggled with getting ambulances quickly to emergencies. In March, a toddler died after choking on a grape after dispatchers failed to send the nearest paramedic. There were several cases last year in which delayed ambulance care led to deaths or prolonged wait times for patients.

After the choking death, the mayor vowed to put an additional 10 ambulances on the street during peak call times. Emergency calls this summer reached a record 579 a day.

The latest incident occurred about 5:20 p.m. on Monday in the 5000 block of Hunt Street NE in Deanwood. Dean said a truck company arrived within four minutes of being dispatched, and an engine within seven minutes. The engine company had firefighters trained as advanced life support paramedics.

Officials said the ambulance was 12 minutes away when dispatched and arrived as firefighters were already taking the infant to the hospital.

Dean said what is critical is that the infant was receiving advanced care quickly. “I concentrate on the medicine,” Dean said. “We had a 1-month-old child in distress. The firefighters made the determination that it was better to transport the patient. We allowed them the option to make that determination.”

Dean said the preference is to not use fire trucks or engines to transport patients, and that he is working through the record call volumes to come up with a solution. He also stressed that too many people are calling 911 when they should be “going to a walk-in clinic.”

This report has been updated.