The Philippe Pinel Institute houses patients with severe psychiatric problems. (CBC)

A psychiatric facility in Montreal is vowing to improve security after a second patient escaped in less than a week.

The Philippe Pinel Institute in east-end Montreal houses people with serious mental problems who, in many cases, have violent histories and criminal records.

A teenaged patient escaped from the Philippe Pinel Institute on Sunday by breaking a 17-centimetre bedroom window.

The patient, who was at Philippe Pinel to undergo psychiatric evaluation, hasn't been found.

Last week, another patient with a violent history escaped using the same method.

Jean-Francois Lussier, 20, broke out of the institute by smashing a bedroom window.

Lussier was being detained at Philippe Pinel after being declared not criminally responsible for a series of violent crimes because of mental illness.

He was picked up by police the next day at a bus station in Joliette, Que.