SALEM, Ore. (AP) — Oregon authorities have closed the state’s entire coastline to mussel harvesting due to an “unprecedented” outbreak of shellfish poisoning that has sickened at least 20 people.

They’ve also closed parts of the Oregon coast to harvesting razor clams, bay clams and oysters.

“We’ve had a paralytic shellfish poisoning event in Oregon that we have never seen in the state,” Matthew Hunter, shellfish program manager for the Oregon Department of Fish and Wildlife, said during a briefing on Friday. The outbreak’s unprecedented nature was due both to the number of species impacted and the number of people falling ill, he said.

Oregon’s Department of Fish and Wildlife and Department of Agriculture announced the new closures Thursday. Elevated levels of toxins were first detected in shellfish on the state’s central and north coasts on May 17, Hunter said.