A massive fire on Sunday ripped through Rio de Janeiro's treasured National Museum, one of Brazil's oldest, in what the nation's president said was a “tragic” loss of knowledge and heritage.

The majestic edifice stood engulfed in flames as plumes of smoke shot into the night sky, while firefighters battled to control the blaze that erupted around 2230 GMT.

Five hours later they had managed to smother much of the inferno that had torn through hundreds of rooms, but were still working to extinguish it completely, according to an AFP photographer at the scene.

By morning the extent of the loss was still unclear.

Firefighters were poised to enter the charred ruins to see what might be salvageable, a fire department spokesman told AFP, adding that it would be dangerous.

“The facade is resistant, but a lot of material fell from the roof,” he said.

“We are going to proceed with great care, to see if we can save something.”

The museum, located in the city's north near the Maracana football stadium, was closed to the public when the fire sparked from a yet unknown cause.

The fire “spread very quickly; there is a lot of inflammable material,” a spokesperson for Rio's fire department told AFP, adding that there were no reports of victims so far.

The natural history and anthropology museum was founded in 1818 by King Joao VI and is considered a jewel of Brazilian culture, with more than 20 million valuable pieces to its name.

“This is a tragic day for Brazil,” President Michel Temer said in a statement.

“Two hundred years of work and research and knowledge are lost.”

“The loss of the collection of the National Museum is incalculable,” he said.

The collection included art and artifacts from Greco-Roman times and Egypt, as well as the oldest human fossil found within today's Brazilian borders, known as “Luzia.”

The museum also housed the skeleton of a dinosaur found in the Minas Gerais region along with the largest meteorite discovered in Brazil, which was named “Bendego” and weighed 5.3 tonnes.

Pieces covering a period of nearly four centuries — from the arrival of the Portuguese in the 1500s until the declaration of the first Brazilian republic in 1889 — were also stored there.

'Culture is grieving'

Brazil's minister of culture, Sergio Sa Leitao, tweeted that “there will be little or nothing left of the palace and the exhibits.”

“The loss is irreparable,” he said. “Culture is grieving. The country is grieving.”

A deputy director at the museum, Luiz Fernando Dias Duarte, voiced “profound discouragement and immense anger” as the treasured institution burned, accusing Brazilian authorities of a “lack of attention.”

He said the museum, a former palace that was once the official residence of the Portuguese royal family, had never had necessary support.

“We fought years ago, in different governments, to obtain resources to adequately preserve everything that was destroyed today,” Dias Duarte told journalists.

The National Museum, which is linked to the Federal University of Rio de Janeiro, has suffered from funding cuts, forcing it to close some of its spaces to the public.

As the flames raged, researchers, professors and university students expressed a mix of sorrow and indignation, with some calling for demonstrations Monday in front of the ravaged building.

'Lobotomy' of national memory

The fire comes as campaigning for October's critical presidential vote gets underway, one of the most uncertain Brazilian elections in decades.

Senator Lindbergh Farias of the country's leftist Workers' Party hit out at the institution's lack of funding and blamed it on spending cuts ordered by the government.

Sa Leitao, who in July 2017 became culture minister under Temer — a deeply unpopular center-right leader — acknowledged that “the tragedy could have been avoided” but said “the problems of the National Museum have been piling up over time.”

The minister recalled that in 2015 under the government of leftist Dilma Rousseff the museum had been closed for maintenance.

Sa Leitao also said the fire struck just after the South American country's National Development Bank had signed a sponsorship contract aimed at revitalization.

He said a reconstruction project would be set in motion, saying “this tragedy serves as a lesson.”

“Brazil needs to take better care of its cultural heritage and the collections of its museums.”

Marina Silva, a former environment minister who is running for president, called the blaze “equivalent to a lobotomy of the Brazilian memory.”

The collection, she said, “contains objects that helped define the national identity — and are now turning to ashes. “