Brazil’s oldest and most important historical and scientific museum has been consumed by fire, and much of its archive of 20 million items destroyed.

The fire at Rio de Janeiro’s 200-year-old National Museum began after it closed to the public on Sunday and was still raging during the night. There have been no reports of injuries, but the loss to Brazilian science, history and culture is incalculable, two of its vice-directors said. The cause of the fire is currently uncertain.

“It was the biggest natural history museum in Latin America. We have invaluable collections. Collections that are over 100 years old,” Cristiana Serejo, one of the museum’s vice directors, told the G1 news site.

Marina Silva, a former environment minister and candidate in October’s presidential elections said the fire was like “a lobotomy of the Brazilian memory”.

The museum was part of Rio’s Federal University but had fallen into disrepair in recent years. Its impressive collections included items brought to Brazil by Dom Pedro I – the Portuguese prince regent who declared the then-colony’s independence from Portugal – Egyptian and Greco-Roman artefacts, “Luzia”, a 12,000 year-old skeleton and the oldest in the Americas, fossils, dinosaurs, and a meteorite found in 1784. Some of the archive was stored in another building but much of the collection is believed to have been destroyed.

Luiz Duarte, another vice-director, told TV Globo: “It is an unbearable catastrophe. It is 200 years of this country’s heritage. It is 200 years of memory. It is 200 years of science. It is 200 years of culture, of education.” TV Globo also reported that some firefighters did not have enough water to battle the blaze.

Brazil’s president, Michel Temer, who has presided over cuts to science and education as part of a wider austerity drive, called the losses “incalculable”. “Today is a tragic day for the museology of our country,” he tweeted. “Two years of work research and knowledge were lost.”

But Duarte said that governments were to blame for failing to support the museum and letting it fall into disrepair. At its 200th birthday in June, not one state minister appeared. “For many years we fought with different governments to get adequate resources to preserve what is now completely destroyed,” he said.

Duarte also said that the museum had just closed a deal with the Brazilian government’s development bank, BNDES, for funds that included a fire prevention project. “This is the most terrible irony,” he said.