Two firefighters were killed and more than 30 people injured after an explosion and fire at a bakery in central Paris.
Ten people had serious but non-life threatening injuries while at least another 37 people had lighter injuries, he said. Castaner later corrected himself in a tweet.
A Paris fire department spokesman says that 36 people, including 12 in critical condition, have been injured in the blast at a bakery that was apparently caused by a gas leak. Some 200 firefighters and police were involved in the operation to contain the situation he said.
She said many residents and tourists have been evacuated from neighbouring buildings and hotels.
"There was broken glass everywhere, storefronts were blown out and windows were shattered up to the third and fourth floors", said 38-year-old David Bangura.
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An employee of a hotel opposite the bakery said he saw the firefighters entering the bakery about an hour before the blast. "And I had just enough time to get down and cover myself and protect my head".
Police believe a gas leak caused the explosion, which happened at around 09:00 (08:00 GMT).
The blast came with the city on edge ahead of expected protests by "yellow vest" anti-government demonstrations, which have often degenerated into violence and vandalism in Paris and other cities in recent weeks.
Police have encouraged members of the public to stay away from the area as emergency services attend to the scene.