Russian President Vladimir Putin has ordered an inquiry into whether enough was done to prevent mass deaths in the southern flood-hit Krasnodar region.
Mr Putin demanded to know how much warning people had been given about the impending disaster.
Activists blamed the ferocity of the flood on the opening of sluice gates at a local reservoir.
A separate criminal investigation is already under way into whether the 144 deaths were caused by negligence.
Officials in the Krasnodar region say two months average rainfall fell in a few hours.
Emergency teams have been sent from Moscow by plane and helicopter. TV pictures showed people scrambling onto their rooftops to escape.
The Krasnodar authorities said altogether 13,000 people had been affected by the floods.
Shipments of crude oil and grain from the Black Sea port of Novorossiysk are suspended.
Russian TV showed thousands of houses in the region nearly completely submerged.
The BBC reports 28cm of rain fell on parts of the region during Friday night, forcing many residents to take refuge in trees or on house roofs.
Many of the dead were elderly people who had been sleeping and drowned. Some were electrocuted while others were swept into the Black Sea.
Monday has been declared a day of mourning.