The cyclone already caused tens of millions of euros (dollars) in damage to the island over the weekend.
Weather services declared a new red alert the highest warning level starting Tuesday evening. A woman was missing after her car was swept away by flood waters, the island's prefect said.
Francois Baroin, French overseas minister, arrived on Reunion Tuesday and said he would stay through the red alert, reports AP.
Baroin already said the French state will pay to reconstruct a bridge that collapsed near the southern town of Saint-Louis over the weekend. The costs were estimated at about EUR20 million (US$26.32 million).