French President Emmanuel Macron has landed on the Indian Ocean archipelago of Mayotte, days after the French overseas territory was hit by a devastating cyclone.

At least 31 people have been confirmed dead so far, but local officials fear the complete toll could be much higher, reaching hundreds or even thousands.

Many parts of Mayotte remain inaccessible after Cyclone Chido – the worst to hit the territory of just over 300,000 in at least 90 years – struck last weekend. The powerful storm flattened neighborhoods, knocked out electrical grids, crushed hospitals and schools and damaged the airport’s control tower.

Mayotte lies in the Indian Ocean off the east coast of Africa, just west of Madagascar. Made up of two main islands, its land area is about twice the size of Washington DC.

The extent of the damage has been difficult to ascertain, in part because of the prevalence of undocumented migrants living in informal dwellings. An estimated 100,000 undocumented migrants, many from neighboring Comoros and Madagascar, live in Mayotte, according to France’s interior ministry.

Mayotte has struggled with poverty, unemployment, violence and a deepening migration crisis, which France has responded to with police crackdowns and mass deportations.

The government activated a state of “exceptional natural disaster” on Wednesday evening, a measure that has never been used, to help manage the crisis, according to the French overseas minister. Authorities also froze the price of consumer goods, such as food and hygiene products, amid shortages.

Local officials have warned that a lack of safe drinking water and poor sanitation conditions could lead to a disease outbreak.

The International Federation of Red Cross and Red Crescent Societies (IFRC) said Tuesday it had lost contact with 200 of its volunteers in Mayotte and that it was racing to deliver aid, including water and medical supplies, to impacted communities.

French authorities distributed 120 metric tons of food Wednesday ahead of Macron’s visit, news agency Reuters reported. On Thursday, the president’s plane also transported more than four tons of food and health aid, Macron said on social media.

Cyclone Chido, a Category 4 storm, tore through the southwestern Indian Ocean over the weekend, impacting northern Madagascar before rapidly intensifying and slamming Mayotte with winds above 220 kilometers per hour (136 miles per hour), according to France’s weather service.

Bruno Garcia, a resident of Mamoudzou, Mayotte’s capital, told BFMTV the destruction was “catastrophic” and “apocalyptic.”

“There is nothing left. It’s as if an atomic bomb fell on Mayotte,” Garcia said.