Japanese online flea-market operator Mercari has banned the sale of pumice stones collected after being spewed forth by the eruption of an undersea volcano, saying their safety has yet to be determined.
There have been many sales of such stones on the Mercari website since late October.
They are believed to have been collected in southwestern Japan's Okinawa Prefecture after drifting there following the eruption near the Ogasawara Islands in August.
In one case, a piece of pumice was on sale for 2,500 yen, or about 22 dollars.
Mercari on Monday banned vendors from putting such stones up for sale. The operator says it's not clear whether the stone is safe because its components have yet to be identified.
Okinawa Prefecture has analyzed pumice stone that reached the coast of Yomitan Village. It says the levels of cadmium, lead and other toxic substances were within acceptable limits under standards set by Japan's government.
Prefectural officials say they are checking stones that washed ashore in other areas. They are calling on people to refrain from collecting pumice stone for the time being.