Somali pirates have freed a Japanese-operated bulk carrier with 21 Filipino crewmen they seized in October, the third ship to be released in a week, Philippine officials said Tuesday.

Vice President Noli de Castro confirmed that the African Sanderling and its crew were released Monday.

The ship was headed to Oman where the crew was to be debriefed before flying home, said De Castro, the presidential adviser on overseas Filipino workers. "Everybody is safe," he added, citing a report by the company that hired the sailors.

The Panamanian-flagged and South Korean-owned ship was seized while en route to Asia from the Middle East.

It was unclear how the ship's release was secured. Foreign Affairs Undersecretary Esteban Conejos said the government was not directly involved in negotiations and added that it does not pay ransoms.

The latest release brought to 44 the number of Filipino sailors on three ships still held by pirates, Conejos said. The Philippines supplies about a third of the world's sailors.

Pirates last year attacked 111 ships and seized 42 off the Horn of Africa. An international flotilla including U.S. warships has stopped many attacks, but the area is too vast to keep all ships safe.

Their biggest prize yet, a Saudi oil tanker, was released last week. Five of the dozens of pirates who had hijacked the tanker drowned Friday when their small boat capsized as they returned to shore in rough weather.

The U.S. Navy released photos of a parachute dropping a package onto the deck of the Sirius Star, and said the package was likely the ransom delivery.

The tanker had a crew of 25. Another ship, the Iranian-chartered MV Delight, also was released Friday with a crew of 25, Iranian television reported last week.

The Sirius Star had been held near the Ukrainian cargo ship MV Faina, which was loaded with 33 Soviet-designed battle tanks and crates of small arms.

Somalia has not had a functioning government since 1991 and its lawless coastline is a perfect haven for pirates. The multimillion dollar ransoms are one of the only ways to make money in the impoverished Horn of Africa nation.