Rescue workers in Japan are beginning a desperate search for survivors after dozens were left dead or missing following widespread flash flooding triggered by record rainfall on the southern island of Kyushu.

Local authorities confirmed at least 18 people had died and 14 were missing in the prefectures of Kumamoto and Kagoshima, with images from the hardest-hit areas showing houses completely destroyed by the strength of the flood waters.

Japan's Meteorological Agency issued a warning Saturday for unprecedented rainfall, calling for residents in Kyushu to take “maximum caution.” At least 270,000 people were told to evacuate in four prefectures across the island.

Kuma Village in Kumamoto saw a record-breaking 83.5 mileometers of rainfall in one hour on Saturday morning, according to the meteorological agency, while Kanoya city in Kagoshima had 109.5 mm in an hour on Monday, its highest ever.

A heavy rain warning remains in place for parts of Kumamoto and Kagoshima on Monday, with more flooding expected.

Officials in Kumamato prefecture said that another 16 people were currently in cardiopulmonary arrest and feared dead, after an elderly care home in Kuma Village was completely flooded when the nearby Kuma River burst its banks on Saturday.

Japan's Self Defense Forces and security authorities are continuing search and rescue operations in Kumamato and Kagoshima prefectures. Efforts have been complicated by conditions on the ground, however, with flooding and landslides cutting off contact to hundreds of communities in the highly-mountainous region.

Speaking at a press conference Monday, Chief Cabinet Secretary Yoshihide Suga said that over 800 people had been rescued so far by emergency services.

According to Japan's Fire and Disaster Management Agency, thousands of households have been isolated and 20,000 firefighters are currently on the ground trying to reach them.

Authorities were using 28 helicopters, four planes and two search ships to survey the area Monday.

Officials told CNN that they are still gathering information on the number of fatalities and expect to update their figures over the coming days.