HONOLULU -- Four containers of Christmas trees from Oregon have been turned back, after slugs were found in some of the holiday cargo.

State plant import specialist Leslie Iseke says the slugs were sent to snail specialist Robert Cowie at the University of Hawaii. He dubbed them potentially serious pests. He says the slugs have been found in Europe, North America and New Zealand.

He says in a temperate place like Hawaii, the slugs would survive by going to higher elevations where it's cooler.

Cowie says they'd be a danger in areas where vegetables are grown.

Officials say each tree container is opened and inspected before going to tree lots.

Sometimes individual trees are pulled for spot checks.

Iseke says fewer containers are contaminated than in years past.