There's a mystery surrounding toxic pollution that's been found on Russia's far eastern coastline.
Where is it coming from?
Greenpeace raised the alarm last week, over what it said looked like an ecological disaster in the Kamchatka region.
Dead sea life has been found on the beach, and surfers have told Reuters they fell ill after getting in the water.
Maya Rudik was one of them.
"First, I felt sandpaper and pain in my eyes, my eyes got red. I had blurry vision after leaving the water for some days, and puffy swelling. Later my sight has got worse, it became hard to see things, even close things. I visited an ophthalmologist, and he said this is a chemical burn of cornea."
The World Wildlife Fund, the conservation group, is now saying that the unexplained toxic pollution was likely caused by a highly soluble substance.
Greenpeace activists also say they found yellowish foam on the ocean's surface, and that the water was murky.
But officials are playing down the scale of the problem, and say the pollution wasn't manmade.
Tests have been carried out on water and land samples.
And both the WWF and Russia's Natural Resources and Environment Minister say it doesn't look like an oil spill.
Vladimir Solodov is the regional governor in Kamchatka.
"For the first time we are faced with this sort of situation, with this kind of pollution. And the fact that we cannot identify it in our labs means that our labs are prepared for other kinds of pollution. From those that we do understand, here in in Khalaktyrsky beach water zone and Big and Small Camp Bays - there is none."
What has caused sea life to die here and surfers to fall ill is proving tricky to work out.
Officials and locals alike are eager for answers.