PORT-AU-PRINCE, Haiti (AFP) — Authorities in Haiti detained a prison guard Monday on suspicion he helped 173 inmates escape in a deadly breakout, a spokesman for the National Police said.

The guard, who worked at the Arcahaie prison northwest of the capital Port-au-Prince, was placed in isolation for his alleged role in the Saturday breakout.

Some of those who escaped are considered armed and dangerous, National Police spokesman Gary Desrosiers told AFP.

Prisons in Haiti — the poorest country in the Americas — are notoriously overcrowded at 450 percent of capacity, the International Center for Prison Studies said earlier this year.

While a majority of prisoners are awaiting trial, all those who fled Arcahaie had been found guilty and were serving sentences, Desrosiers said.

Around 20 of them were serving more than ten years, he added.

Police are on the lookout for the escapees, but have recaptured only 10 so far.

A preliminary investigation indicates that a guard “forgot” to lock a door Saturday as the inmates were eating. The prisoners left the cafeteria and armed themselves with police weapons, a source said on condition of anonymity.

The escapees killed the head prison guard and wounded two others during the ensuing firefight.

With only one rifle missing from the prison arsenal, it appears the inmates stripped the prison guards — all National Police agents — of their weapons, Desrosiers said.

Arcahaie will remain empty while the investigation continues, with all remaining inmates moved to a different prison, he added.