Authorities say a mysterious orange-colored substance has washed up on the shores of a remote village in northwest Alaska.

Tests have been conducted on the substance on the surface of the water in Kivalina (KIV'-uh-LEE'-nuh). City Administrator Janet Mitchell told The Associated Press that the substance has also shown up in some residents' rain buckets.

Coast Guard Petty Officer David Mosely tells KTUU that it's not a petroleum substance and it's not man-made. Mitchell says the village is requesting that an algae expert from the University of Alaska Fairbanks investigate.

Pictures taken by resident Mida Swan show an orange sheen across the harbor and on beaches in the village about 625 miles northwest of Anchorage.

Swan says she didn't smell anything odd when she dipped her hand into the substance.