Parts of the islands, which were struck by Cyclone Chido over the weekend with winds of more than 200km/h, remained inaccessible to rescue workers on Monday, said French civil security spokesperson Alexandre Jouassard.
"The next minutes and hours are very important," he told France 2 TV. "We are used to working in these conditions, and a few days after, you have pockets of survivors."
Asked about the death toll of several hundred, the French interior ministry said "it will be difficult to account for all victims" and said a figure could not be determined at this stage.
Cyclone Chido was the strongest to strike Mayotte in more than 90 years, French weather service Meteo France said. It has a population of about 321,000 and is made up of two main islands over an area about twice the size of Washington.
— Gendarmerie nationale (@Gendarmerie) #Chido 🌪� Soutien aux Mahorais et à nos camarades mobilisés à #Mayotte. Des renforts de gendarmes seront déployés sur place pour appuyer les équipes engagées. pic.twitter.com/iiDAjcgprUDecember 15, 2024
French President Emmanuel Macron was due to hold an emergency meeting about Mayotte later on Monday, France's BFMTV reported.
The wreckage of hundreds of makeshift houses was strewn across hillsides. Coconut trees had crashed through building roofs and hospital corridors were flooded, according to images from local media and the French gendarmerie.
"It was the wind, the wind blowing, and I was panicked, I screamed 'We need help, we need help", I was screaming because I could see the end coming for me," John Balloz, who lives in the capital Mamoudzou, told Reuters.
With water supplies cut, residents queued outside grocery stores on Monday in search of bottled water and basic provisions, residents told French television stations.
After Mayotte, Chido made landfall in north Mozambique. It quickly weakened and was reclassified as a tropical storm on Sunday but still destroyed several houses, authorities said.
Cyclone Chido was the strongest to hit Mayotte in more than 90 years. (AP PHOTO)
The full extent of casualties and damage in Mayotte, which lies between Mozambique and Madagascar, remained unclear.
The prefect of Mayotte, Francois-Xavier Bieuville, said at the weekend that deaths would definitely be in the hundreds and possible several thousand.
Establishing the toll was made harder as some people quickly buried loved ones in accordance with Muslim tradition.
Images from Mayotte showed boats upended, cars buried under rubble and people cowering under tables when the cyclone hit.
Located nearly 8000km from Paris, Mayotte is a major destination for undocumented immigrants from nearby Comoros. It is significantly poorer than the rest of France: three in four people live below France's national poverty rate.
Maritime and aerial operations were underway to transport relief supplies and equipment, including from Reunion Island, another French overseas territory, French authorities said.
Mayotte's main airport, however, remained closed to civilian flights on Monday morning, said Jean-Paul Bosland, the president of France's national firefighters' federation.
French Health Minister Genevieve Darrieussecq told BFMTV that floodwaters had been evacuated from Mayotte's central hospital but that the conditions there were still difficult. She said 100 health reservists were being deployed to Mayotte.
Eric Coquerel, who leads the French parliament's finance committee, said the destruction in Mayotte laid bare a failure to prepare for the consequences of climate change.
"Living conditions (in Mayotte) are completely unsanitary for many," he told French broadcaster LCI.
"It was evident that ... when a cyclone hit ... we would find ourselves in a situation."
with DPA