A spokesman for replacement mayor Alexandre Duplessis said the mayor felt he was the victim of an extortion attempt and reported the June 14 incident to police.
He did not, however, confirm two media reports that the complaint to police was triggered by a dispute with an escort over payment.
"The mayor's confirming that there's been an extortion attempt against him," said mayoral spokesman Pierre-Philippe Lortie.
"He immediately called the authorities. As we speak, it's in their hands."
The case represents only the latest controversy involving a Canadian mayor following resignations, criminal charges and police investigations of municipal leaders in different cities.
Duplessis himself replaced a predecessor who resigned amid corruption allegations and, next door in Montreal, a fellow replacement mayor resigned last week after being arrested on corruption charges.
Police did confirm they were investigating an extortion allegation involving an escort.
When asked specifically about news reports involving the Laval mayor, provincial police confirmed they were investigating an extortion attempt against someone in Quebec — but would not name the person who filed the complaint.
"A man used an escort service," said police spokeswoman Sgt. Christine Coulombe. "There was a fight about the payment, then a complaint was filed about extortion. We're investigating."
The police spokeswoman would not say whether the case involved Duplessis: "We never confirm the identity in a situation like this," she said.
She said she expected the case would be sent to prosecutors for their consideration.
Radio-Canada cited police sources saying that the dispute allegedly began when one of two women, an escort and her driver, recognized the mayor. It reported that he allegedly cancelled their appointment, triggering an argument about payment.
Duplessis has already been plunged into controversy during his brief reign.
His city was placed under provincial trusteeship this month after a witness at a corruption inquiry said Duplessis took part in illegal political financing.
Duplessis had recently been named to the interim post as his predecessor, longtime Laval mayor Gilles Vaillancourt, resigned in scandal and was slapped with gangsterism charges.
He is also the second interim mayor in the Montreal area to wind up in a major controversy.
Michael Applebaum stepped down in Montreal after he was arrested and charged with fraud over municipal land deals. This was barely seven months after he replaced the last Montreal mayor, Gerald Tremblay, who resigned amid allegations of illegal political financing.
There are no charges against Tremblay. He denied the allegation, and his accuser has since admitted to making up other details on the witness stand at the provincial corruption inquiry.
In Laval, when Duplessis requested provincial trusteeship on May 31, he made a brief statement and answered just one media question.
He was asked whether he intended to remain mayor and said that he planned to stay until the November election.
"I will continue my mandate. . . However, I remain realistic," Duplessis said. "The current context has me reconsidering my candidacy for the mayoralty in November."
The alleged extortion incident occurred two weeks later.