MONTREAL—Two men were hurt Friday after an ambulance hit a car, caught fire and exploded in the dead of night.

The chain reaction that led to the incident began at 3:30 a.m. when a driver on Highway 20 westbound near Cartier Ave. hit a road sign then plowed into construction cones.

“At 3:30 a.m. an impaired driver collided with a mobile road sign and cones on Highway 20 westbound just near Cartier and a good Samaritan happened by and stopped to give some assistance,” said Surete du Quebec spokesman Daniel Thibaudeau.

Shortly thereafter, the good Samaritan was rear-ended by the ambulance. The two paramedics suffered minor injuries and were taken to hospital for treatment.

“Both paramedics were transported out of precaution, they had no visible injuries. But as we do for all our patients who are involved in an accident we always want to take them to hospital,” said David Sasson of Urgences-Sante.

After the Urgences Sante technicians got out of their ambulance the vehicle caught fire which resulted in several explosions. Since the damage was already so extensive, firefighters left the vehicle to burn rather than risk injury.

Accident investigators are trying to understand why the ambulance caught fire. Sasson speculated that the oxygen tanks in the ambulance were the cause of the blasts.

The highway was closed while the two cars and the remains of the ambulance were taken away, with traffic flowing again just before the morning rush hour.

The Surete du Quebec arrested the 25-year-old driver of the first car for drunk driving and will be recommending charges. The driver was released on Friday, but must appear before a judge within three months.