The biggest science museum in Europe, Cite des Sciences et de l'Industrie began to burn between 02:30 and 03:00 am local time on Thursday.
There is no official information on cause of the fire and no one seems to know how it started.
According to iTele, a French digital channel, the fire started in a showroom and a movie theatre then reached the six floor.
The blaze affected about 10,000 square meters of the museum's territory in central Paris.
According to French media, authorities immediately engaged 120 firefighters and 30 vehicles to extinguish the blaze. Two firefighters were slightly affected by the fire.
After six hours, the blaze was finally controlled by the firefighters.
Cite des Sciences et de l'Industrie in Paris is the biggest science museum of Europe and visited by five million people every year.
The building is a steel truss construct which was halted in 1973. On September 15, 1980, construction designed by two architect, Adrien Fainsilber and Peter Rice was commissioned.
It was opened on March 13, 1986, inaugurated by Francois Mitterrand upon the occasion of the encounter of the Giotto space probe with Halley's Comet.
Classified as a public building of an industrial and commercial character, the museum has a planetarium, an entire submarine and an IMAX theatre.
Cite des Sciences et de l'Industrie will be closed on Thursday due to recovery efforts.
Cité des sciences will be exceptionally closed today, thanks for your understanding
— Cité des sciences (@citedessciences) August 20, 2015
Social media and some news agencies tweeted about the fire in their personal accounts.
— enlighfr (@enlighfr) August 20, 2015
— France Bleu 107.1 (@FBleu1071) August 20, 2015
— B.Illy (@BenjaminIlly) August 20, 2015