Investigators in Panama discovered two Soviet-era MiG-21 fighter jets aboard a North Korean cargo ship that was seized this month as it tried to pass through the Panama Canal after departing from Cuba.

According to the Associated Foreign Press, the fighter jets were found alongside missile and other weapons parts concealed in a shipment of sugar. Possession of the hidden weaponry could constitute a violation of tough U.N. sanctions on Pyongyang.

Cuban officials claim the Chong Chon Gang, a rusting, 14,000-metric-ton ship that carries a painted North Korean flag, was sending the "obsolete" weapons to North Korea to be refurbished and returned.

Javier Caraballo, Panama's top anti-drugs prosecutor, told Reuters the planes gave off a strong odor of gasoline, indicating that they had likely been used recently.

MiG-21 Fighter Jets Panamanian forensic workers close a container holding a MiG-21 fighter jet seized from the North Korean-flagged ship Chong Chon Gang during investigations at the Manzanillo Container Terminal in Colon city Sunday. Photo: Reuters

U.N. sanctions experts plan to travel to Panama to inspect the shipment on Aug. 5 once Panama has finished unloading the 510-foot ship.

In related news, North Korea has asked Panama to release the ship and its 35 member crew, who were arrested and charged with attempting to smuggle undeclared weapons through the canal. North Korea has insisted the shipment is entirely legitimate.

Panama has so far dismissed North Korea's requests.

MiG-21 Fighter Jets Found On Seized North Korean Ship