Priceless artifacts spanning 11,000 years went up in flames as an inferno swallowed Brazil's National Museum.
More than 20 million pieces of history, including Egyptian mummies and historic artwork, may have been destroyed.
"The loss of the National Museum's collection is insurmountable for Brazil," President Michel Temer tweeted.
No one knows what sparked the blaze around 7:30 p.m. Sunday. Firefighters worked through the night to battle the flames, but a museum official said the damage is already "irreparable."
"Very little will be left," preservation director Joao Carlos Nara told Agencia Brasil. "We will have to wait until the firefighters have completed their work here in order to really assess the dimension of it all."
保护主任Joao Carlos Nara告诉巴西通讯社，“应该剩不下什么了，我们只能等消防员完成他们的工作之后，再好好评估损失。“
So far, no serious injuries have been reported. Most of the human toll came in the form of grief and tears as employees, researchers and academics flocked to the scene in Rio de Janeiro.
"This is 200 years of work of a scientific institution -- the most important one in Latin America," "Everything is finished. Our work, our life was all in there."
The palatial National Museum building used to be the home of a Portuguese royal family. Almost exactly 200 years ago, it was converted into a museum.
Since then, the National Museum has become Brazil's oldest historical institution and an internationally prominent research center.
The museum housed 20 million artifacts in areas such as biological anthropology, archeology, ethnology, geology, paleontology and zoology, according to its website.
One of the museum's most famous artifacts is known as "Luzia," the skull and bones of a 25-year-old woman who died more than 11,000 years ago. They are the oldest remains ever discovered in Brazil, the museum's website says.
Minister of Culture Sergio Sa Leitao said the country "is in mourning."
文化部长Sergio Sa Leitao说整个国家都笼罩在悲伤之中。
"I have also asked for a complete evaluation of the fire preparedness conditions of every other federal museum in the country," he said, "in order to verify the steps that need to be taken to avoid another tragedy."