An archive of more than 20 million items is said to have been destroyed in Sunday's fire at National Museum of Brazil.
There have been no reports of any casualties in the blaze at the 200-year-old museum in Rio de Janeiro, but museum officials have described the loss to Brazilian science, history and culture as incalculable.
President Michel Temer said it was a sad day for all Brazilians, adding two hundred years of work, investigation and knowledge have been lost.
The museum contained artifacts not just from Brazil, but also from ancient Egypt, Greece and Italy and it was also home to "Luzia," the oldest human fossil to have been found in the Americas.
While the cause of the blaze is still under investigation, government cuts and inadequate fire protection systems have been cited as possible factors.
Brasilia had cut spending on culture and education to make up for the billions of dollars spent on the Rio Olympics.