India’s National Museum of Natural History has been gutted by an early morning fire in central Delhi. The fire broke out on the top floor of the FICCI building in which it is housed, gutting parts of the museum. Most of its valuable artefacts, including a dinosaur fossil, are believed to have been lost.

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The 38-year-old museum focused on India’s flora and fauna, conservation and environmental education, and was especially popular with school children.

The museum had been conceptualised by former prime minister Indira Gandhi in 1972, the 25th anniversary of India’s independence. Its collection included a 160 million-year-old fossil bone of a sauropod, bird eggs, preserved butterflies, stuffed animals and birds, herpetological specimens and dioramas.

WATCH: Fire which broke out at Delhi's Natural History Museum at around 2 am today morning (earlier visuals)https://t.co/ygh6K86G4Y — ANI (@ANI_news) April 26, 2016

Natural History Museum(Delhi) fire: Smoke and flames still billowing out from a section of the building's top floor pic.twitter.com/PmmlXgbHrc — ANI (@ANI_news) April 26, 2016

“The fire at the National Museum of Natural History is tragic. The museum is a national treasure… the lost cannot be quantified,” India’s environment minister Prakash Javadekar tweeted.

The fire broke out in the early hours of Tuesday morning, and is likely to have started from electrical equipment. It took over four hours and 35 fire tenders to douse the flames. No one was present inside the building when the fire started. According to fire officers, the building’s fire safety mechanisms were not working. Javadekar has now ordered a fire safety audit of 34 museums in the country.

On Twitter, several people mourned the loss of the museum.

Horrid to see Delhi 's Natural History museum gutted in a fire. Million childhood memories tied to it. Was right next to my school as well — barkha dutt (@BDUTT) April 26, 2016

Irreparable loss.Entire Natural History #Museum in Delhi gutted in a #fire. — kishalay b (@kishalay) April 26, 2016

Huge fire reported @ Delhi's National Natural History Museum; dread to think what treasures we may have lost; such places shld be fire-proof — Uma Sudhir (@umasudhir) April 26, 2016