Prime Minister Shinzo Abe has made his way through disaster-struck areas of Ehime Prefecture, which was one of the hardest hit regions in the record downpours that devastated western Japan.
Abe visited an evacuation center in Ozu City on Friday, a week after torrential rains battered the area.
He said the government will do everything it can to help the evacuees, who are suffering greatly.
The prime minister also met with Ehime's Governor, Tokihiro Nakamura, who requested continued support from the Self-Defense Forces. Nakamura also asked for help in restoring infrastructure, including water supplies.
On Saturday, torrents of mud went gushing through the streets of Ozu after authorities made the decision to release water from 2 upstream dams that were filled to capacity with rainwater. The move caused thousands of tons of water to pour out of the dams every second.
Four people died. 4,600 homes were damaged.
Residents along the river say they had little time to prepare for the surge in water levels.
City officials say they used an emergency warning system to alert people that the waters were coming. But some are questioning that claim.
Abe said the land ministry will investigate the warning system and make any changes necessary as soon as possible.
The prime minister also said the Cabinet's website will provide updates on efforts to restore water supplies and transportation services in affected areas.