An undocumented alien was captured Thursday outside the Honolulu immigration office.

Only this was the four-footed kind. Specifically, an opossum.

It is unclear why a young marsupial was outside the U.S. Immigration and Customs Enforcement building, 595 Ala Moana Blvd., near Piers 1 and 2.

But opossums are known to hitchhike in cargo containers, and there are plenty in the area.

The marsupial was seen running loose, then crawling into the engine compartment of a Dodge Avenger, which appeared to have been parked there for some time, said Keevin Minami, a land vertebrate specialist at the Department of Agriculture’s Plant Quarantine Branch.

“The most funny part was it was at immigration,” he said.

Immigration officials called quarantine inspectors to capture the opossum at 8 a.m. outside the U.S. Immigration and Customs Enforcement building.

Opossums are native to North America and are omnivorous, eating insects, eggs, rodents, fruit and vegetables. They are less likely to carry rabies than other mammals but are carriers of parasites and other diseases, the Agriculture Department said in a news release.

The opossum was given a rabies test as a precaution, and the quarantine branch is awaiting the results of the test, which was sent to Kansas, Minami said.

This was not the first of its kind to arrive in Honolulu.

In July 2012 an opossum was caught in a cat trap at a Sand Island warehouse, and in August 2011 one was found in a shipping container being unloaded in the Ward Center area.

In 2005 one was discovered in a military cargo plane at Hickam Air Force Base. Another was found the same year in the mail receiving area at the U.S. Postal Service facility at Honolulu Airport.

Anyone who sees or knows of illegal animals is encouraged to call the state’s pest hotline at 643-PEST (7378).