Police in a northern Mexico state have detained a corrections officer and four inmates in the investigation of a prison fire that killed 14 inmates last week.

Officials in Nuevo Leon state initially said the Friday blaze at a prison on the outskirts of Monterrey may have been caused by a short circuit. But on Sunday they ruled it arson.

The Nuevo Leon government said Monday that state police are holding the five suspects as they investigate possible motives and how the fire started.

A spokesman says the detained officer has told police the fire broke out after a fight among 59 inmates. The spokesman says five of the 14 inmates who died showed bruises and marks on their heads and chests.