A prisoner has escaped from the Montée St-François Institution, the second inmate to vanish from the minimum security federal prison in Laval this week.

Officials at the institution discovered Meloche went missing during a head count at the institution on Sunday night.

"These occurrences are extremely rare; they do not happen often. Of course, every time we look at the circumstances that have led these individuals to escape, we take the corrective actions to prevent them from happening again," said Serge Abergel, spokesman for Correctional Service Canada.

Meloche, 56, has been serving a sentence since Sept. 13, 1980 for second degree murder, attempted murder, forcible confinement, theft and armed robbery.

Authorities said anyone with information on his whereabouts should contact police.

Correctional Services Canada has teamed up with the prison, the Sûreté du Québec and Laval police to conduct an investigation and apprehend the suspect.

Philippe Pelletier, 32, also went missing from the institution on Wednesday.

He was incarcerated in November 2010 and is serving a six-year sentence for theft, conspiracy to commit an indictable offence, possession of a weapon and disguise with intent.

Earlier this week, Alex Michaud-Robitaille was apprehended after having escaped the Sainte-Anne-des-Plaines Institution, another minimum security prison in Laval.

He was serving time for possession of stolen goods, obstructing a peace officer, misdemeanor and driving under the influence.

"These are individuals who have been evaluated as being at low-risk to public safety, as such, they were in minimum safety institutions. The perimeter of a minimum safety institution is defined but it's not directly controlled unlike maximum and medium security institutions," said Abergel.

Authorities did not comment on how any of the men managed to escape the prisons.