The web-based ride service is under close investigation by the city's Taxi Bureau after months of criticism from politicians and taxi drivers.
The two UberX drivers face $350 fines and require a judge's approval to have their cars returned to them.
"An UberX driver is not allowed to work in Montreal because he's doing illegal transportation, because they don't have a permit to offer transport in exchange for money," said Benoît Jugand, General Manager of the Montreal Taxi Bureau.
He said to be legal, taxi drivers must complete 150 hours of training, pass an exam and pay $180,000 for a permit.
Seizures within transport laws
Quebec Transport Minister Robert Poëti maintains that the vehicle seizures are well within the province's transport laws, and will continue.
"The law is there and they have to follow the law… we are allowed to do that and we are going to do it. Yes, for UberX, I'm going to do it," he said.
Officials from UberX say special legislation is needed to regulate their services.
"Montreal should be spending their time and money sitting with us and finding solutions for a service that people really want and not spending citizens' taxes and police officers' time seizing vehicles on the platform," said Jean-Nicolas Guillemette, General Manager of UberX Montreal.
Not a taxi service
The company insists it's not a taxi service, but a ride-sharing arrangement that costs a third less than regular taxis.
UberX was launched in Montreal last October, and Guillemette says so far the program has been successful.
"It's growing really fast. We have tens of thousands of Montrealers that are using it every week," he said
UberX says this cuts the numbers of cars on the road and reduces drunk driving.
Guillemette says the company has made repeated requests to meet with Denis Coderre, but so far the mayor has refused.