A suspected spillage of toxic chemicals on the coast of far east Russia has wiped out almost all marine life on the area’s seabed, scientists have said. Divers who inspected the waters off a 25-mile stretch of Kamchatka peninsula reported that 95 per cent of creatures on the ocean floor were dead; findings they said confirmed fears of an “environmental disaster” with a potentially devastating long-term impact.

In early September, the water changed colour to a greyish-yellow, with a thick milky foam on the surface, and a strong foul smell filled the air. A few days later, octopuses, seals and other sea creatures began to wash up on the beach. The local authorities at first dismissed the reports. But amid mounting pressure, Russia’s Investigative Committee Wednesday launched a criminal probe into suspected violations in the use of environmentally hazardous substances and waste and marine pollution. In a meeting with Kamchatka Governor Vladimir Solodov, local scientists reported that the majority of marine life on the seabed was dead.

Some scientists speculated that rocket fuel may have leaked out of the sites’ storage facilities. Underwater photographer Alexander Korobok, who took part in an expedition, said: “After this dive, I can confirm that there is an environmental disaster. “The ecosystem has been significantly undermined and this will have long-term consequences, since everything in nature is interconnected.”

It is still unclear what caused the contamination. Initial probes showed that levels of phenol, a substance often used as antiseptic or disinfectant, were 2.5 times higher than normal, and petroleum levels 3.6 times higher. Local media outlets have speculated about a possible oil tanker leak or military drills gone wrong, which the Defense Ministry denied. “The investigators are checking all possible sources of pollution, including the territories of landfills adjacent to the Avachinsky Bay and the coastal strip of Khalaktyr where toxic chemicals are stored,” the Investigative Committee said in a statement.

Russia’s environment minister, Dmitry Kobylkin, earlier downplayed the reports and said: “For us, there is no scale of the disaster. “No one has died, no one was hurt.” It came after Greenpeace and the World Wide Fund for Nature voiced their concern for the region. But recently, Mr Kobylkin changed tone and vowed that those responsible for the pollution would be punished.

That is the newest in a string of ecological disasters Russia has seen in recent times, coming 4 months after 20,000 tons of gasoline from a broken tank poured into a close-by river within the Siberian metropolis of Norilsk.