An official says a massive fire has gutted India's National Museum of Natural History in New Delhi, one of the country's top museums.

Harinder Singh, a fire official, says firefighters took more than four hours to douse the blaze, which started early Tuesday on the top floor of the six-story museum. Thirty-five fire engines were called.

Singh says the entire building was gutted by the blaze.

Environment Minister Prakash Javadekar says the damage caused to the museum was being assessed. An investigation into the cause of the fire has been ordered.

Singh says five firefighters overcome by a heavy smoke were taken to a hospital and released after being treated.

The state-run museum features exhibits on plants, animals and mineral wealth in India.