By Tom Balmforth and Vladimir Soldatkin
MOSCOW (Reuters) - Conservation group WWF said on Monday that unexplained toxic pollution off Russia's far eastern coast was likely caused by a highly soluble substance as officials played down the scale of the problem and suggested it was not manmade.
Greenpeace raised the alarm last week over what it said looked like an ecological disaster off the coast of Kamchatka region, reposting images of dead sea life washed up on the coast. Surfers said they fell ill after getting into the water.
On Monday, Greenpeace said activists had found yellowish foam on the ocean's surface in several places and dead sea animals in one location, and that the water was murky.
"A slick, or rather some kind of volume as it's not only on the surface, but also deep down, is moving along the coast," said activist Vasily Yablokov.
Alexei Knizhnikov of the WWF said the pollution did not look to be the result of an oil spill.
"It's very likely to be a highly toxic contamination by a very soluble substance because organisms on the seabed were also affected," he said.
People who got into the waters off Khalaktyrsky beach complained of sore throats, worsening eyesight, dry eyes, nausea, physical weakness, vomiting and fever, Greenpeace said.
Natural Resources and Environment Minister Dmitry Kobylkin said initial tests of water and land samples showed no evidence of elevated levels of oil or oil products and played down the scale of the problem.
"You asked what the scale of the disaster is - for us, there is no scale of disaster. No one has died, no one was hurt," he was quoted as saying by RIA news agency.
"I was talking to the guys - eight surfers wrote they received cornea burns of the eye, but in fact this can be treated with eye drops. This is not a severe burn," Kobylkin said.
He added the pollution did not appear to be manmade in origin.
Dmitry Lyasov, a surfer, said many people at a local surfing camp had fallen ill after getting into the water.
"I didn't vomit, but dozens have done, and then they had fevers of up to 38 Celsius and body pain. And I'm now seeing double. I had good eyesight, but now after seeing a doctor I've been told my sight has got worse."
(Additional reporting by Anastasiya Lyrchikova; Editing by Mark Potter)