RIO DE JANEIRO (AFP).- The fire that devastated Brazil's National Museum in September was caused by the air conditioning system and spread quickly because the building lacked the equipment to contain it, federal police said Thursday.

Ricardo Saadi, chief of the federal police, made the announcement at a news conference at which he ruled out arson.

"The fire broke out in the auditorium and main cause was the installation of air conditioning," he said, explaining the system did not meet the manufacturer's recommendations on the use of individual circuit breakers and grounding devices.

The auditorium, which is located on the ground floor of the four-story former imperial palace, was the first room destroyed by the fire, which took six hours to contain.

With the exception of fire extinguishers, the museum didn't have the equipment to help contain the blaze, including alarms, fire houses or fire doors, according to the investigation.

The National Museum fire on September 2, 2018 wiped out much of the collection, dealing a hard blow to the main showcase of Brazil's anthropological heritage and history.

Since then, dozens of anthropologists, archeologists and paleontologists have spent nine hours a day, six days a week combing through the ashes and charred structure. The facade still stands, though all that was inside and most of its roof were destroyed.

Among the recovered relics are fragments of "Luzia" -- the fossilized, 12,000-year-old remains of a human considered the centerpiece of the museum's collection.

There is also a five-ton meteorite called Bendego that survived the blaze, as well as some fragments of a dinosaur, Maxakalisaurus topai.

© Agence France-Presse