(AP) — An 85-year-old American veteran of the Korean War has been detained in North Korea since last month.

The son of Merrill Newman told the San Jose Mercury News on Wednesday his father was taken off a plane set to leave North Korea on Oct. 26. Jeffrey Newman said no reason was given.

Newman, from Palo Alto, Calif., was traveling with Bob Hamrdla, who was allowed to return. In a statement, Hamrdla said it was “a terrible misunderstanding” and asked the North Korean government to quickly release his friend.

The U.S. State Department wouldn’t confirm the detention, and North Korea’s state media has yet to comment.

The detention comes about a year after North Korea detained another American. The State Department recently warned Americans against travelling to the country.

North Korea has detained at least six other Americans since 2009.