WATCH: Woman caught using a cellphone at the wheel — on a highway, at 120 km/h

The Sûreté du Québec says it's investigating after someone in a car on Highway 15 in Laval caught a motorist travelling at 120 km/h — with a cellphone in her lap.

The video has been viewed more than a million times since it was posted last Friday. It shows a woman at the drivers' seat peering intently at her phone screen, appearing to get ready to send a text message.

The person who shot the video — apparently, from a passenger seat — also managed to catch the woman's licence plate number.

The SQ is asking for anybody who may have witnessed the incident to come forward.

Meanwhile, they're also reminding people that if you witness anyone committing a road infraction, to contact police immediately.

WARNING: The video contains strong language.