MONTREAL -- Eight people, including a former high-ranking Montreal city councillor, were arrested Tuesday and charged with running a kickback scheme whereby engineering companies would allegedly be awarded city contracts in exchange for political donations and other favours.

The investigation was conducted by Quebec's anti-corruption unit, known as UPAC, which said in a news release it targeted about 30, mainly engineering contracts valued at $160 million, awarded by the City of Montreal between 2001-09.

UPAC alleged a network of engineering firms, elected officials and municipal workers had developed "a system of sharing contracts."

Engineering firms were awarded $160-million worth of contracts between 2001-09 in exchange for political donations, kickbacks and "other personal favours," UPAC said in a statement.

UPAC struck in the morning and arrested Frank Zampino, a former chairman of Montreal's powerful executive committee, Robert Marcil, a former Montreal public works director and Bernard Trepanier, a fundraiser for the defunct municipal Union Montreal party.

Also arrested were several former engineering bosses with Cima+, Teknika HBA and Groupe SM.

UPAC announced Tuesday afternoon an eight person, Bernard Poulin -- the founder of Groupe SM -- was taken into custody.

The charges against the eight suspects include fraud and conspiracy to commit fraud, municipal corruption and breach of trust.

Zampino is currently on trial for fraud and breach of trust in a separate case, stemming from a deal for a housing project dubbed Faubourg Contrecoeur, built on what was once city-owned land.

UPAC said the investigation began in 2014 and the arrests on Tuesday were one phase of a larger, ongoing investigation.