Somalia’s Galmudug state helped secure their release on Thursday, local official Omar Sheikh Ali said by phone. He didn’t say whether any ransom was paid. The four were among crew taken hostage at sea on April 18, 2010, the United Nations envoy to Somalia, Nicholas Kay, said in a e-mailed statement.

“They’ve gone through a long-time horrific ordeal in which their captors often used torture,” Ali said.

The mission to recover the hostages, who were seized from a Taiwanese-flagged fishing vessel, was undertaken by the UN Office on Drugs and Crime, funded by the Contact Group for Piracy off the Coast of Somalia’s Trust Fund, Kay said.

Pirates seized a total of 24 crew members, six of whom succumbed to illness in captivity, while 14 Burmese nationals were released and repatriated in May 2011, according to Kay. Pirates used the boat as a mother ship until it capsized in July 2011 and the remaining crew were moved ashore, he said.

Somali pirates are still holding at least 26 hostages, Kay said, urging their release “without further delay.”