The number of victims remains unclear several says since cyclone made landfall, and authorities fear hundreds or more could have been killed.
President Emmanuel Macron is expected to visit the French territory of Mayotte in the Indian Ocean as it reels from the strongest storm to hit it in 90 years.
The president said he will arrive in the archipelago, which is France’s poorest territory, on Thursday and declared national mourning after ensuring “continuity of the state”.
So far, 22 deaths have been confirmed in Mayotte, but there are fears the actual toll from Cyclone Chido could be much higher.
“I cannot give a death toll because I don’t know. I fear the toll will be too heavy,” acting Interior Minister Bruno Retailleau told BFMTV on Wednesday.
Newly appointed French Prime Minister Francois Bayrou said on Tuesday that more than 1,500 people were injured, including more than 200 critically.
Authorities fear hundreds, or possibly thousands, could have been killed by Chido, which made landfall on Saturday and devastated the islands.
Some of the victims are believed to have been buried before their deaths were included in official tolls, and authorities are still unable to reach some areas to bury the bodies.
The situation is made more complicated because officials are uncertain about the actual population of Mayotte. Official figures put the population at 321,000, but many believe it is much higher due to undocumented immigration.
Many of the migrants are believed to be among the victims because some were living in unsafe conditions in shantytowns, which were devastated by winds reaching speeds of 200km/h (124mph).
Chido also killed at least 34 people in Mozambique and 13 in Malawi after hitting continental Africa.
The French government has been sending food and other assistance to Mayotte with about 100 tonnes expected to be distributed on Wednesday on the larger island of Grande-Terre and another 20 tonnes on the smaller island of Petite-Terre.
Meanwhile, a curfew went into effect on Tuesday night from 10pm to 4am to prevent looting and lawlessness.
Retailleau said two gendarmes were injured overnight by projectiles during the curfew.
The destruction caused by Chido has also raised concerns about an epidemic and spread of dangerous diseases such as cholera.
International aid and rescue groups have said it is imperative to ensure access to clean water to help prevent the spread of diseases. But some of the healthcare centres on the islands have also been damaged, making it more difficult to mount a coordinated response to the cyclone.
The government has released an initial 655,000 euros ($687,000) to finance urgent needs with Paris Mayor Anne Hidalgo pledging a further 250,000 euros ($262,000) from the city’s emergency fund for recovery efforts.
Internet observatory Netblocks reported on Tuesday that connectivity remains low after the cyclone tore through Mayotte, flatlining at just 16 percent of ordinary levels.
“The telecoms disruptions are likely to impact search, rescue and aid efforts and prevent loved ones from contacting each other,” it said.