HAGATNA, GUAM—Authorities in the U.S. territory of Guam have turned away a ship after thousands of spiders overflowed from its cargo.

The Guam Department of Agriculture says hundreds of large spiders and thousands of smaller ones were seen when stevedores began offloading insulation and beams for housing units from the ship, the M.V. Altavia.

The cargo was returned to the ship, and the Agriculture Department on Friday ordered that the ship not be allowed to dock. It was last ported in South Korea.

Agriculture officials say they don’t know what type of spiders were on the ship, but said it’s a type that isn’t normally found on the island.

They said there was concern the spiders could damage Guam’s environment.

The ship was carrying housing units and accessories for a work force village expected to house up to 18,000 temporary workers.

Information from: Pacific Daily News, www.guampdn.com