Tokyo (CNN) Hundreds of thousands of people in southwestern Japan have been ordered to evacuate their homes as torrential rain continues to hit the region.

Authorities issued an emergency alert Wednesday, warning of mudslides, flooding and swollen rivers in Fukuoka, Saga and Nagasaki prefectures in Kyushu island. The agency initially issued its highest level alert, known as a level five, but later downgraded it to a level four.

A total of 870,000 people living in the area have been ordered to evacuate, as of 3:30 p.m., local time Wednesday.

The heavy rain, which started on Tuesday, has seen some areas hit by more than 100 mm (4 inches) of rainfall in an hour, public broadcaster NHK said. More rainfall is expected throughout Wednesday, according to the country's Meteorological Agency.

Rising water caused by heavy rain is seen at Muromi river in Fukuoka on August 28, 2019.

An elderly man was found dead after his car was washed away by floodwater in Takeo city, Sage Prefecture, Wednesday, according to the Fire and Disaster Management Agency, while two more people were seriously injured.

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