Bernard Theberge, who was outside on the bar's patio at the time of the crash, feared for the safety of those inside the popular Musi-Cafe when the first explosion went off.
"People started running and the fire ignited almost instantaneously," he said.
"It was like a movie," said Theberge, who considered himself fortunate to escape with only second-degree burns on his right arm.
"Explosions as if it were scripted — but this was live."
Firefighters, including some from Maine, doused the blaze for hours. Local fire chief Denis Lauzon described the scene as one akin to a war zone.
Dozens of residents gathered hours after the explosion at the edge of a wide security perimeter and many feared the worst. About a kilometer (0.6 miles) down the town's main street, flames danced around a railway tanker that sat at the edge of the road.
"On a beautiful evening like this with the bar, there were a lot of people there," said Bernard Demers, who owns a restaurant near the blast site. "It was a big explosion. It's a catastrophe. It's terrible for the population."
Demers, who fled his home, said the explosion was "like an atomic bomb. It was very hot. ... Everybody was afraid."
Charles Coue said he and his wife felt the heat as they sprinted from their home after an explosion went off a couple of hundred yards (meters) away.
"It went boom and it came like a fireball," he said.
Another resident Claude Bedard described the scene of the explosions as "dreadful."
"The Metro store, Dollarama, everything that was there is gone," he said.
Environment Quebec spokesman Christian Blanchette said a large but undetermined amount of fuel had also spilled into the Chaudiere (Ah-DER-Re) River. Blanchette said the 73 cars were filled with crude oil, and at least four were damaged by the explosions and fire.
"We also have a spill on the lake and the river that is concerning us. We have advised the local municipalities downstream to be careful if they take their water from the Chaudiere River."
He added that a mobile laboratory had been set up to monitor the quality of the air.
Firefighters and rescue workers from several neighboring municipalities, including Sherbrooke and Saint-Georges-de-Beauce, were called in to help deal with the disaster.
Firefighters from northern Maine were also deployed to the Quebec town, according to a spokesman at the sheriff's office in Franklin County.
Prime Minister Stephen Harper expressed his sympathy in a statement.