A fire has gutted the National Museum of Brazil in Rio de Janeiro, the oldest scientific institution in the country.

Most of the 20 million items it contained, including the oldest human remains discovered in the Americas, are believed to have been destroyed.

Firefighters are working to put out the blaze. No injuries have been reported.

The museum, which once served as the residence for the Portuguese royal family, celebrated its 200th anniversary this year.

The fire started on Sunday evening, after the facility had closed for the day. The cause is not known.

Aerial images broadcast on Brazilian television showed it spreading throughout the building.

Brazil's President Michel Temer said in a tweet that it was a "sad day for all Brazilians" as "200 years of work, research and knowledge were lost".

Roberto Robadey, a spokesman for the Rio fire department, is quoted by AP news agency the hydrants closest to the museum were not working and that firefighters had to get water from a nearby lake.

He added that some of the museum's pieces had been rescued.

What did the museum contain?
Among the 20 million items it housed were archaeological artefacts, fossils and the largest meteorite discovered in the country.

The natural history collection included dinosaur bones and a 12,000-year-old skeleton of a woman known as "Luzia", the oldest ever found in the Americas.

The building was also home to items covering the centuries from the arrival of the Portuguese in the 1500s to the declaration of a republic in 1889, as well as a vast archive on Brazil's indigenous communities.

Portugal's royal family transferred the court to the building in 1808, when the country faced with the threat of invasion from Napoleon.

Art and artefacts from Greco-Roman times and Egypt were also on display at the museum.

What has the reaction been?
Marcelo Moreira - a journalist with TV Globo in Rio - told the BBC: "It's very sad... This museum has a great history. It represents a lot for Brazilian history and Brazilian culture. It's really a big loss for Brazil."

In an interview with Globo, the museum's director said it was a "cultural tragedy".

One museum employee told the network that project managers had had "tremendous difficulty" trying to secure funding for "sufficient" resources for the palace.

Another, librarian Edson Vargas da Silva, is quoted by local media describing the building, which he said had wooden floors and contained "a lot of things that burn very fast", such as paper documents.

Employees had reportedly previously expressed concern about funding cuts and the dilapidated state of the building.

The institution was established in 1818 as the Royal Museum with the aim of promoting scientific research by making its collection available to specialists.