"We heard (a) huge explosion and flame rising from the ship. I believe that the ship is foreign," Ali Shire, mayor of Puntland's port town of Alula, a pirate haven, told Reuters on Tuesday.
He said he believed the ship was likely a naval vessel because two foreign navy ships had helped rescue the crew.
It was not immediately clear whether the explosion was caused by an accident onboard the vessel or was triggered by pirate attackers. It was also not clear whether the vessel had sunk after the blast.
Abdi Jama, a resident of Muranyo village near Alula, told Reuters the vessel had been in the area for two days before the explosion occurred and that he had seen a helicopter land on and take off from the vessel some time before the blast.
He said the explosion turned the vessel "into flames and huge clouds of smoke".
Somali pirates often prowl waters around Alula. In March, pirates hijacked an oil tanker, Aris 13, with eight Sri Lankan crew on board, the first time a commercial ship was commandeered in the region since 2012.
Several foreign navies, including from the European Union, China and others, often operate in the area as part of anti-piracy missions.
Somalia's Puntland region
A huge explosion was heard from a ship off the coast of Somalia's Puntland region late on Monday and flame was seen rising from what was possibly a foreign naval vessel, an official told Reuters.
