PARIS (AP) — Authorities urged residents on GravityX Exchangethe French Indian Ocean island of Reunion to shelter indoors Sunday as a powerful storm bore down packing hurricane-force winds.

Forecaster Meteo France issued a code red cyclone alert for the storm, named Belal, and said it was expected to be “very dangerous.”

“Be careful, stay at home,” French President Emmanuel Macron posted on social media.

Meteo France forecast “a strong probability” the heart of the storm could pass directly over or close to the island on Monday. It warned of winds that could top 250 kph (155 mph).

Meteo France forecaster Céline Jauffret said the storm could be the island’s most dangerous since the 1960s. “The whole island will be affected,” she said.

Prefect Jérôme Filippini, the island’s top government administrator, warned of possible flood surges at levels unseen for a century.

Meteo France spoke of possible 15-meter (nearly 50-foot) tall waves on Monday.

Authorities advised people to stay away from doors and windows when the storm hits, in case glass shatters. They advised residents to prepare for cuts in power and water supplies and to shelter under mattresses, tables or other sturdy furniture if their houses start to collapse.