A North Korean ship that was stopped in Panama last year for carrying undeclared Cuban weaponry, was crossing the Panama Canal again on Wednesday after a clean inspection.

The Chong Chon Gang, in Panama after visiting Cuba again, was inspected thoroughly, and with no violations, started crossing the canal en route for home, canal administrator Jorge Quijano said.

"The boat has already been boarded. It has undergone an extremely thorough inspection and nothing of concern was found," Quijano said. The sugar freighter was due to finish the crossing Thursday.

In July 2013, after docking in Cuba, the ship was stopped on suspicion of carrying drugs as it tried to enter the canal, the busy waterway linking the Caribbean and Pacific.

A search by Panamanian authorities uncovered 25 containers of Cuban military hardware, including two Soviet-era MiG-21 aircraft, air defense systems, missiles and command and control vehicles.

The containers were concealed under more than 200,000 sacks of sugar.

Both Havana and Pyongyang said the weapons were obsolete Cuban arms being shipped to North Korea for refurbishment under a legitimate contract and due to be returned to Cuba.

But neither country explained why the shipment was hidden if it was indeed legitimate.

Panama held the boat for months before finally releasing its crew; North Korea was fined a million dollars for endangering the canal but actually paid $700,000.

In addition, Panama asked the United Nations to send a mission to determine if the attempted shipment violated a UN embargo on arms deliveries to North Korea.

The results of the mission's probe have not been made public. But Panama authorities say the UN team's report confirms the cargo violated the embargo.