MONTREAL -- The technical problems Montreal's transit authority (STM) has been experiencing across its online platforms have turned out to be linked to a ransomware attack. 

The agency said on Wednesday the attack occurred "despite the various defenses that are in place to deal with this type of event." 

"It should be remembered that thanks to robust security devices, the bus and metro network service as well as the sales and collection equipment are operating normally," it added. 

The STM announced it was experiencing issues on Tuesday, citing a computer virus before announcing that it had been a ransomware attack. 

Service was and still is up and running across the bus and metro network, but accessing schedules and other information online may not be possible at the moment. Paratransit services have been impacted as well -- and only trips for medical purposes are being carried out at this time. 

"The paratransit service, whose reservation platform is computerized, is having a greater impact," the agency said. "Travel for medical and work reasons will therefore be honoured as of October 21, for reservations made before 9:15 p.m. on October 18. In addition, no travel reservation or modification will be made." 

"Our teams are working to restore the situation as soon as possible," the STM wrote on Twitter. 

As for accessing scheduling information, the agency is suggesting for customers to use partner applications such as Transitapp and Chrono instead.