Crews unloading a North Korean-flagged ship detained in the Panama Canal for carrying undeclared arms from Cuba have found live munitions on board, a Panamanian official said Friday.

Explosive-sniffing dogs found ammunition for grenade launchers and other unidentified types on munitions, said anti-drug prosecutor Javier Caraballo, who did not specify the amount of munitions.

The ship, Chong Chon Gang, was headed from Cuba to North Korea when it was seized in the canal July 15 based on intelligence that it may have been carrying drugs.

The manifest said it was carrying 10,000 tons of sugar, but Cuban military equipment was found beneath the sacks. No drugs have been found so far.

After the seizure, Cubans officials said the cargo included 240 metric tons of obsolete planes and missiles they were sending to North Korea to be repaired and returned. There was no mention of munitions or explosives in the government statement, and Cuban officials could not be reached immediately for comment Friday afternoon.

“We don’t have a sheet or a list to determine if what we’re finding corresponds to that specified by the Cuban government,” Caraballo told reporters.

He said the munitions boxed were closed and would have to be examined by explosive experts to determine the amount and types.

The weapons discovery triggered an investigation by the U.N. Security Council committee that monitors the sanctions against North Korea. The council is sending a team to see if it violates U.N. sanctions. Panama earlier this week asked to postpone the visit to Aug. 12 because it is taking so long to unload the ship.

As of Friday, crews had only unloaded two of five cargo holds in the ship. Besides the munitions, they had found radar and control systems for launching missiles, two Mig-21 aircraft and 12 motors, all previously specified by the Cuban government.

Panama has filed charges against the crew for transporting undeclared military equipment.

North Korea is barred by the U.N. from buying or selling arms, missiles or components, but for years U.N. and independent arms monitors have discovered North Korean weaponry headed to Iran, Syria and a host of nations in Africa and Asia.

The U.N. says North Korea also has repeatedly tried to import banned arms. Analysts say it maintains a thriving sideline in repairing aging Warsaw Pact gear, often in exchange for badly needed commodities.

The North Korean government has not commented on the seizure except to ask that the crew be set free.