MOSCOW, September 2 (RIA Novosti) - Russia has extended an investigation into a fatal accident at a Siberian hydropower plant until September 15, the federal industrial safety regulator said on Wednesday.

The date has been put back "due to a need for additional checks and studies," Rostekhnadzor said.

Seventy-three bodies have been found and two people remain unaccounted for following the accident at the Sayano-Shushenskaya plant on the Yenisei River in south Siberia on August 17.

A surge of water burst into the turbine hall, completely destroying three turbines and flooding several lower stories of the plant. The exact cause of the accident remains unknown, and several leads are being investigated.

A special investigation committee has opened a criminal investigation into possible violations of work safety regulations.

Russia's crumbling infrastructure, underfunded since the 1990s, has often been the cause of industrial accidents, costing thousands of lives.

State-controlled RusHydro, which owns the hydropower plant, has said repairing the damage could take up to two years, and Energy Minister Sergei Shmatko estimated the cost at over 40 billion rubles ($1.2 billion).