Investigators say the fire started in a gutted ambulance around 2:15 a.m. in Ardmore. It was parked inside the volunteer medical service corp of Lower Merion and Narberth on the 100 block of Sibley.
Officials say the smoke alarm went off while the crew was on duty and they called 911.
Firefighters arrived to heavy flames in the rear of one of the ambulances.
The fire quickly went to two-alarms.
The fire has forced some first responders out of their home base in Ardmore Friday, and it could be several days before operations return to normal.
"One of our trucks was a significant loss," said Chief of Operations Christopher Flanagan.
The fire was contained to the one truck, but four more vehicles sustained smoke damage.
"The ambulance fleet is unfortunately out of service need. It's going to need to be decontaminated, cleaned, and then certified by Montgomery County EMS inspectors for state licensure," said Christopher Flanagan, Chief of Operations.
A two person crew was in the building but they weren't injured. They heard the smoke alarms and evacuated.
Firefighters contained the blaze, but the damage was already done and was costly.
"An ambulance itself is around $190,000, and the equipment goes to $80,000. The heart monitor is around $126,000; all of that was a total loss, and that just the one vehicle that was damaged," said Flanagan.
Mutual aid agreements were already in place. Other municipalities helped with EMS protection in the area.
Crews were up and running using loaner equipment from other stations including Haverford.
The cause of the fire is under investigation, but it does not appear suspicious.
"The entire back bay of one of the ambulances is completely burned out, so obviously the area of origin is in there. It is our intent to remove that vehicle from the building tonight to take it to a secure location to do a further investigation," said Lower Merion Fire Chief Chas McGarvey.
There is also smoke and water damage to the building so they will have to relocate for about a week."We are probably going to call a lot of volunteers from the area who are calling already to help. We are going to need a major undertaking to get this place cleaned up<" said Flanagan.