Oregon State Police are warning people to look out for military marine markers that have been washed up on the beach. They're silver canisters about 18 inches long and 3 inches wide.
Last week, three of them were found along the Oregon coast.
State Hazardous Device Technicians say it is not uncommon to respond to one a month, but three in a week is very unusual.
The devices are dropped by military aircraft to mark the location of something floating in the ocean. The trouble is, they contain white phosphorous, which burns in contact with air.
State police are warning people because they could ignite spontaneously and cause significant damage.