The tragedy at a power plant hit by deadly flood last week was Russia's biggest technological catastrophe in 25 years, the emergency situations minister said Wednesday, comparing it to the Chernobyl nuclear disaster.

"This is the greatest technological accident for the last 25 years, the largest one on many counts -- on the scale of damage, on the loss to our energy industry, and naturally, to the economy," Sergei Shoigu told Moscow Echo radio.

However, unlike Chernobyl which led to the nuclear plant's closure, the Sayano-Shushenskaya dam "can and must be restored", Shoigu said.

"If in Chernobyl it was understood that restoring it is hard and it must be properly sealed up, here I for one am sure that it will be restored," he said.

The Sayano-Shushenskaya dam was hit by flooding on August 17, killing 69 people. Six more are missing and presumed dead.

Investigators have said a technical fault triggered flooding in the plant's turbine room. The dam's owner RusHydro has ruled out human error for the accident.

But authorities have still not given a conclusive explanation of what happened, saying several theories remain under consideration.