MONTREAL -- A witness at Quebec's corruption inquiry has described how his car was once blown up when he ran afoul of an asphalt cartel.

Gilles Theberge was a director at Sintra, a construction company that was one of four partners in a cartel that controlled the supply of asphalt around Montreal.

He says they conspired to jack up the price 30 per cent higher than what would have been charged under a free-market system.

He says he quit his company after some dramatic events on June 15, 2000.

Theberge was jolted at 2:45 a.m. by a loud crackling -- which was the sound of his car blowing up.

Instead of calling the police first, he says he called his boss to quit and say that the collusion had gone too far.

He says he also called construction magnate Tony Accurso, another member of the alleged four-company asphalt cartel. Accurso, the longtime head of a sprawling construction empire, has come up repeatedly at the inquiry.

He was allegedly also involved in a sewage cartel, according to key witness Lino Zambito, and allegedly had a corrupting influence on politicians, with paid vacations and trips on his yacht. Previous inquiry testimony has alleged that he has Mafia ties.

Theberge says he called his powerful ally to ask if he knew anything about the car bomb. He says Accurso told him he'd heard nothing about it.

The previous day, Theberge and a number of other construction types had gathered at Accurso's new restaurant in Laval. He says one of the other men, Joseph Borsellino, had asked him if he planned to compete for a $4 million contract in the municipality of St-Laurent.

Theberge recalls replying that it was neither the time, nor the place, to discuss such things. Borsellino made it clear, he says, that Sintra should bow out of the bid.

The men agreed to pick up the discussion at a later point. They never got the chance, because Theberge quick his job immediately after the explosion.

Theberge has shared other anecdotes about how intimidation was used to keep the corrupt system in place.

One time, he says, a Mafia-linked man nicknamed "Mr. Sidewalk," Nicolo Milioto, came to tell him that the broken window's at his next-door neighbour's house were a warning.

He says Milioto told him the intention was to break the windows at Theberge's own house -- "but the guy got the wrong house."

He says he sometimes received late-night phone calls, with no one on the other end of the line, when a bid was due. He also says another construction boss told him about a bomb placed under his car, too.

Theberge says he concluded that it was generally easier to say yes to his competitors, and recuse himself from a bid, in order to keep the peace.