UNITED NATIONS — North Korea said Wednesday that Mexico had “forcibly detained” one of its ships for months after the vessel ran aground in the Gulf of Mexico, and the North blamed the United States for blocking the ship’s release.

But the coordinator of a United Nations panel of experts said that the ship, the Mu Du Bong, was owned by a North Korean company that was under United Nations sanctions and should be “frozen” and that the panel had received excellent cooperation from Mexico in tracking the company and its assets.

“In the case of the Mu Du Bong, the evidence is overwhelming,” the panel’s coordinator, Hugh Griffiths, wrote in an email. The United Nations sanctions were imposed in response to North Korea’s nuclear and missile programs.

Sanctions were imposed on the ship’s owner, the Ocean Maritime Management Company, in July after the Panamanian authorities found two Cuban fighter jets, missiles and live munitions beneath a cargo of sugar in another ship the company operated.