Newly-released audiotapes show Tom Harding was stunned to learn his train had rolled down the tracks and exploded.

The recordings reveal the panic and confusion MM&A train engineer Tom Harding felt when he first learned that his train was responsible for the inferno that killed 47 people in Lac-Megantic.

Most of the details about what occurred that night are already known. On the audiotapes Harding can be heard informing dispatchers when he parked his train, and informs them exactly how many handbrakes he set.

A second phone call happens when the engine train catches fire, and Harding volunteers to return to the train to make sure everything is safe, but is told to stay at his hotel.

The next call comes at 1:47 a.m., after the explosion in the centre of Lac-Megantic forced an evacuation of most of the town.

Harding tells the supervisor the town is on fire, and that police believe a natural gas line has burst and caught fire.

Two hours later, at 3:29 a.m. Harding is told the devastating news that the explosion was caused by the train he had been driving.

"It's worse than that my friend," said the dispatcher RJ.

"Why?"

"It's your train that rolled down."

"No," said Harding in disbelief.

"Yes sir."

"No RJ."

"Yes sir."

"Holy fuck. Fuck," said Harding.

Harding's lawyer, Thomas Walsh, said the recordings show his client was concerned about the train and acted responsibly.

"He didn't have any doubts about how well the train was secured, it's not like when he learns there's a big fire there it's not like he said- gee maybe that's my train because I didn't secure it very well," said Walsh.

"As far as he was concerned it was well secured and as the TSB report points out the 7 brakes is a ten percent rule of thumb that he has always used there and never had any problems with it."

Harding, along with Jean Demaitre and Richard Labrie, were charged with 47 counts each of criminal negligence causing death in May 2014.

Earlier this week the Transportation Safety Board said no single person was to blame for the derailment that destroyed a section of the town of Lac-Megantic, instead linking the majority of failures to poor government oversight and lax safety standards at MM&A.