Quebec's BEI -- the Bureau of Ethical Investigations -- is looking into a deadly police chase.

Just after 4 a.m. Tuesday Terrebonne police started chasing three vehicles, one of which was stolen, on Highway 640.

Police caught the first driver, the second driver escaped, but the third driver kept going at high speed until he entered Mascouche and crashed into a tree.

The crash killed an 18-year-old passenger, although the 18-year-old driver is expected to survive life-threatening injuries.

Police then informed the BEI of the crash, and the agency sent nine investigators to the scene at 7:50 a.m. Tuesday.

The investigators are asking all witnesses to contact them at