EASTPORT, Maine — A Dutch ship which had completed loading bales of wood pulp on Wednesday was stopped from leaving port Thursday night by the U.S. Coast Guard, which said it is investigating a possible oil spill.

Roland “Skip” Rogers, the general manager of Federal Marine Terminals, said the incident was unusual for Eastport, which expected to see 18 ships this year.

“This has never happened here before,” he said Friday. He said rumors that the ship was seized or under armed guard were not true.

“The tugs are here, the pilot is here, the crew is free to go, but the ship cannot leave,” he said.

The ship, the Margit Gorthon, flying under the flag of the Netherlands, was undergoing an intensive inspection all day Friday, according to U.S. Coast Guard Unit Controller Ken Stuart out of Portland.

“We are investigating a marine pollution incident,” he said, which he categorized as a possible oil spill. He said the investigation continued all day Friday and was not completed. It will continue Saturday.

Stuart did not know how much oil might have been spilled.