Rescuers at one of Russia's largest diamond mines were searching early on August 5 for eight miners still missing after a water cavern collapsed into an underground shaft with 142 workers inside.
One miner was reportedly rescued on August 5 and was taken to a local hospital in "weak" condition, officials said.
After the water broke through into the Mir mine in the Sakha region early on August 4, 133 of the workers were safely evacuated and a search was launched for the nine missing miners, Alrosa, Russia's largest diamond producer, said.
Yegor Borisov, head of the Sakha region, was quoted as saying the water levels in the mine were stable and ventilation and electrical systems were working. Therefore, he said, there was hope the remaining miners were still alive.
Russia's Emergency Situations Ministry declared a state of emergency in the town of Mirny near the mine some 4,160 kilometers east of Moscow and said an offiical search and rescue mission was under way.
The ministry's head, Vladimir Puchkov, said 32 mine rescuers and seven mine divers had arrived at the scene.
Interfax reported that communications was established at one point on the night of August 4 with two or three of the trapped miners.
The water flooded into one of the mine's pumping stations from a crater where water discharges had been disposed that contained some 300,000 cubic meters of water -- the equivalent of 120 Olympic-size swimming pools, the ministry said.
Alrosa said it was an "uncontrolled increase in the flow of water" out of the abandoned crater into the underground shaft.
It said the flood was caused by sudden and unexpected geological processes and the washing away of rocks in the crater. It insisted that all of the mine's "equipment has been regularly tested."
One company official told TASS that it was fortunate the massive water release occurred at the start of the work shift before many miners had descended deep into the mine where the water flowed.
The Sakha region's branch of the Russian Investigative Committee said it was checking into possible safety violations at the mine.
The director of the mine, Mikhail Lopatinsky, has reportedly been suspended pending the results of the investigation.
Russian television said the rescue operation at the Mir mine was hindered by a power cut that prevented the lift system from working.
TV channels showed footage posted on social media of water flooding into a control room and coming from the ceiling of underground passageways.
Of the 133 people evacuated from the mine, two were taken to a hospital with minor injuries, the region's Health Ministry said.
Russian President Vladimir Putin, who visited Siberia on August 4, was briefed about the accident, his spokesman, Dmitry Peskov, told TASS.
Alrosa's president, Sergei Ivanov, flew to the scene, as did Sakha region head Borisov, who brought along doctors specializing in emergency medicine.
Emergency Situations Minister Puchkov also traveled to the scene.
Ivanov, 36, is the son of Putin's former chief of staff, also named Sergei Ivanov. He has headed Alrosa since March.
Alrosa, based in the Sakha region, made a net profit of 22.7 billion rubles ($376.37 million) in the first quarter of 2017.
The Mir mine was launched in 2009 and produces 1 million tons of diamond ore per year. Last year, the diamonds it produced totaled 3.19 million carats, according to the company's website.
Until 2001, Alrosa used open-cast mining at the Mir site, which has been used for diamond production since 1955. The open-cast mine is a vast round crater with a diameter of over 1 kilometer that is one of the largest man-made holes on Earth.
TASS reported that the Mir mine was hit by a smaller emergency last week when a rockslide buried a loading machine and killed a miner.
The last major mining accident in Russia resulted in 36 people being killed by methane explosions that ripped through the Severnaya coal mine north of the Arctic Circle in February 2016.
In 2010, 91 people died after a methane explosion at the Raspadskaya coal mine in the Siberian region of Kemerovo.
With reporting by AFP, TASS, and Interfax