Russian officials failed to give adequate warnings before flash floods that killed at least 171 people in the southern Krasnodar region, the Russian government says.
President Vladimir Putin has demanded a full report by the weekend on the disaster and how it was handled.
A day of mourning is being held for the victims. Record torrential rain has been blamed for the floods.
The town of Krymsk was devastated and the district boss has been sacked.
Seventeen people are still missing after Friday night's disaster. Russian media say 210 people are in hospital, including 48 children.
Emergencies Minister Vladimir Puchkov said there had been warnings but "not all the population was warned in time".
"Mistakes were made by local leaders and various services," he said.
Local officials say flood warnings were given using sirens, sms messages and loudspeakers. But many people were asleep at the time and did not hear them.