The fire broke out around 1.45 AM on the top floor of the museum, located in FICCI Building in Mandi House, where some repair work was underway. It quickly spread to all other floors of the building. As many as 35 fire tenders were pressed into service.
It took firefighters more than four hours to douse the blaze after which a cooling operation was launched which lasted for another few hours, a fire official said.
The cause of the fire is yet to be ascertained, a senior police official said. There were not too many people in the building, which was evacuated by the time fire officials reached at the scene.
Six fire officials were rushed to hospital after they inhaled excessive smoke during the operation. Their condition is said to be stable now, the official said.
Top officials of the police range and Delhi Fire Services rushed to the spot to take stock of the situation. The damage caused by the fire is being estimated. Established in 1972, the National Museum of Natural History in New Delhi is one of two museums focusing on nature in India. It functions under the Ministry of Environment and Forests.