Three Greeks and one Philippino seafarers from a tanker attacked by Pirates off Nigeria were freed after almost four weeks in captivity, Greek authorities announced on Wednesday.

Greece’s Merchant Marine Ministry didn’t reveal the name of the ship involved but it is understood to be the 16,500-dwt chemical tanker Madonna I (built 2008), which was boarded by intruders on 5 March.

Piraeus-based Atlantic Management, the ship’s managers, declined to comment.

The four abducted crew members were released on 28 March and were all in good health, the ministry statement said, citing information received from the ship’s management company. All of them have returned to their homes.

The Madonna I was underway ballasting off Boney Island when an estimated ten pirates approached in a black speedboat firing, and then boarded the ship with a grappling hook and ladder.

Twenty-two crew members and one representative of the ship’s owners were on board at the time of the attack. The pirates then left the ship with the four abducted crewmembers.

A string of vessels has been recently attacked off Nigeria and in the Gulf of Guinea. The 6,430-dwt Sampatiki (built 2008) is said to have been the latest piracy victim, with five of its crew members kidnapped.

 On Friday, Bourbon Offshore confirmed that two crewmen kidnapped from one of its anchor handlers off Nigeria in late February have been freed.