MONTREAL - Could a fiery turf war be erupting between the Toronto Mafia and its brethren in Montreal?

Montreal police say that's one hypothesis they're examining as they probe a rash of firebombings that have targeted mainly Italian establishments in their city.

Deputy police chief Jacques Robinette, head of special investigations, said Tuesday that the last arson incident dates back to Jan. 25, but there's no evidence the attacks are over.

Police are examining several theories, including a surprising one about a Montreal-versus-Toronto Mafia rivalry.

"There are a lot of hypotheses that have been put out there," Robinette said after a news conference on street-gang activity in Montreal.

"There is the hypothesis of two different Mafia clans, two Mafia clans of the same background, Mafia versus street gangs, and it's possible that all of those hypotheses could be right, too."

One of those theories is that Calabrian Mob groups based in Toronto could be trying to gain a foothold against Montreal's destabilized Sicilian clan.

The once-dominant Rizzuto family faced few challenges since the early 1980s. But, recently, they have been besieged with a succession of legal woes, and by the murder of reputed boss Vito Rizzuto's eldest son.

Robinette said no theory has been discounted, while a team of more than 20 investigators of major crimes, arson, and street gangs looks into the cafe attacks.

At first glance, Robinette said, the attacks could appear to stem from a battle over drug trafficking. But there is also a clear attempt at intimidation in each of them, he added.

None of the 18 reported incidents resulted in heavy damage or death.

"It's only for now, as far as we're concerned, intimidation," Robinette said.

Experts weighing in on the arson wave and the slaying of Rizzuto's son, Nick, in late December believe rivals are lining up to replace the once-mighty Montreal mob.

Most of the clan's top lieutenants are behind bars, and Vito Rizzuto himself is serving out a prison term in the United States until 2012.

Among the possibilities being floated by experts is that street gangs were responsible. An 18-year-old man with ties to street gangs is the only person to be charged so far in the firebombings.

But Robinette said another possibility is that street-gang members are acting as hired help in the Mafia battle.

Police released data Tuesday that suggested gang-related crime is down on the whole in Montreal.

In an annual report, police cited a change in how the gangs are functioning. Long-standing rivalries between groups defined by their gang colours is giving way to a single, unifying colour: the colour of money.

"The colour of the group you belong to is secondary to the profit that is to be had," Robinette said.

There are an estimated 300 to 500 gang members in Montreal.