At least 324 people have died in the Indian state of Kerala since the start of monsoon season in late May, officials said on Friday.

In just the past 10 days, flash floods and landslides have killed 164 people in the southern state, authorities said earlier on Friday, as torrential monsoon rains continued to batter Kerala. Half of those deaths have occurred in the past three days, State Relief Commissioner P.H. Kurian told CNN.

The flooding is the worst Kerala has experienced in nearly a century.

The death toll has steadily risen over the past week as rescue workers scramble to reach thousands of people stranded by floodwater. The army, navy and coast guard have been sent in to assist, and fisherman have been asked to help with rescue efforts.

Thirteen of Kerala’s 14 districts remain under a red alert, the highest warning level issued during emergencies in India, according to the country’s National Disaster Response Force (NDRF), which has deployed 53 teams across the state.

Kurian is hopeful that the weather will soon improve. “The rain will let up by tomorrow,” he said Friday. “Areas will still be inundated but we will have some relief.”

Over a thousand personnel from military and disaster authorities are now involved in the rescue mission. Meanwhile, over 100,000 people have been forced to seek shelter in relief camps, Rekha Nambiyar, senior commandant in India’s National Disaster Response Force, told CNN.

Search and rescue efforts have been further complicated by limited transport; railway tracks and roads are too flooded to use, and operations at the international airport in the city of Kochi have been suspended until Saturday.

Indian Prime Minister Narendra Modi, who had asked the defence ministry to step up relief and rescue operations, announced Friday that he would visit Kerala that evening to “take stock of the unfortunate situation.”

Monsoon rains are to be expected in India this time of the year. But after days of abnormally heavy rains, 34 of the state’s 40 dams reached full capacity and were opened to release water in an effort to prevent potentially disastrous breaches, officials said today.

“There was a 40-50% excess of monsoon rains this year and because of the incessant rains, there have been landslides and entire areas inundated under water,” said Nambiyar of the NDRF.

The Indian Meteorological Department (IMD) has reported that heavy rains are expected to continue until Saturday.

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