The Danish oil tanker, seized by pirates in the Gulf of Guinea, has been located after a frantic search, with a portion of the crew having been abducted, Monjasa, the ship's owner, announced Friday.

The Monjasa Reformer, which had 16 crew on board when it was boarded by pirates on March 25, was found on Thursday by the French navy off the coast of Sao Tome and Principe.

When the vessel was located, "the pirates had abandoned the vessel and brought a part of the crew members with them," Monjasa said in a statement.

"The rescued crew members are all in good health and safely located in a secure environment and receiving proper attention following these dreadful events," it said.

No details were provided on the number of crew kidnapped or their nationalities.

"Our thoughts are with the crew members still missing and their families during this stressful period," Monjasa said, adding that it was "working closely with the local authorities" to obtain the sailor's safe return.

The owner said there was no reported damage to the vessel or cargo.

The 135-meter-long Monjasa Reformer "experienced an emergency" on March 25 around 160 miles (260 kilometers) west of Port Pointe-Noire in the Republic of Congo, Monjasa said.

The shipowner added that the crew had sought refuge in the tanker's secure room or "citadel" when the pirates boarded, "in accordance with the onboard anti-piracy emergency protocol".

The vessel was "sitting idle" at the time of the incident.