A misunderstanding between a District paramedic and a dispatcher may be why a 90-year-old woman had to wait more than 45 minutes to be transported to a hospital after collapsing at her Southeast Washington home Tuesday, D.C. fire officials said.

Firefighters, trained as paramedics, used a fire engine to take the woman to a Prince George’s County hospital. Authorities did not disclose her medical condition. Typically, ambulances and advanced life-support paramedics arrive within about eight minutes of being called.

The case is the latest in a string of problems facing the D.C. fire department, which has come under intense scrutiny in the past two years. Both D.C. Council members who are running for mayor in November have said embattled Fire Chief Kenneth B. Ellerbe needs to be replaced.

The department is still reeling from the death in January of Medric Cecil Mills Jr., 77, who collapsed across the street from a fire station but was denied help from the firefighters inside. The lieutenant in charge of the station retired before being disciplined. Hearings are scheduled next month for others involved.

Among cases in 2013, a heart attack victim died after waiting 29 minutes for an ambulance; a D.C. police officer who was struck by a car waited 15 minutes with a broken leg before being taken to an emergency room by a medic from Prince George’s; and an elderly man who suffered a stroke was transported in a fire engine because the nearest ambulance was seven miles away.

The latest incident, first reported Tuesday night by WTTG (Fox 5), occurred about 2:15 p.m. Tuesday and involved a call to an apartment in the 3700 block of D Street SE, in the Fort Dupont area.

Three officials with knowledge of the incident said it appeared that Medic 21 was mistakenly dispatched to take the 90-year-old woman to the hospital even though that unit was on another call. When the crew radioed that it was transporting a patient, the dispatcher thought it meant the 90-year-old and assumed the call had been handled, according to the officials, who asked not to be identified because an investigation into the incident is ongoing.

In a statement, the department said it appeared that fire personnel “mistakenly indicated that they were available to respond but in fact were not available.”

“A decision was made to immediately transport the patient to the closest hospital using a fire truck. It’s important to note that assistance was rendered quickly to the patient . . . until care was transferred to the hospital,” it said.

Neither the woman nor her relatives could be reached for comment Wednesday.

Fire authorities said they are trying to determine why it took so long for anyone to realize a mistake had been made. A spokeswoman for the D.C. Office of Unified Communications, which oversees the dispatch and 911 call center, declined to comment.

John Sullivan contributed to this report.