A fire in the 15-century cathedral in the western French city of Nantes blew out stained glass windows and destroyed the grand organ on Saturday, and officials said they suspected arson.

Prosecutor Pierre Sennes told reporters three fires had been started at the site and authorities were treating the incident as a criminal act.

Officials said an investigation had been opened.

The fire began in the early morning, engulfing the inside in massive flames, and dozens of firemen brought it under control after several hours. Smoke was still coming out of the Gothic structure later on Saturday morning.