Pirates attacked a container ship off the coast of Nigeria and kidnapped five crew members on Thursday, while pirates kidnapped four crew members of a different ship on Wednesday.

The International Maritime Bureau, or IMB, reported the pirate attack near the area of Brass, Nigeria, in the Bayelsa State. Fourteen heavily armed pirates in two ships, a speedboat and a supply boat attacked the container ship. Upon being boarded, the ship’s crew sounded the alarm and went to the ship’s citadel, a ship’s safe room that can protect the crew from such attacks. The pirates breached the citadel and kidnapped five of the ship’s crew members, including the master and commanding officer.

The pirates escaped with the five crew members and the ship’s cash. The remaining crew was reported safe, according to the IMB report.

Security sources speaking to Reuters identified the ship as the City of Xiamen from Antigua and Barbados. The identities of the five hostages remain unknown, but Reuter’s source said the container ship’s crew consisted of Sri Lankans with two foreign crew members, one hailing from Russia and the other member from Myanmar.  

The container ship was released by the pirates on Saturday, Vesseltracker.com reports. It remains unclear if the pirates hijacked the ship for its cargo in addition to taking hostages, as the report notes the period of time the pirates held the ship was longer than is customary for a kidnapping scenario.

Pirates attacked two other ships off the coast of Nigeria on Wednesday, according to IMB reports. In one incident, pirates aboard a speed boat fired upon a container ship, but the ship was able to thwart being boarded with increased speed and escaped the pirates. In a pirate attack off the coast of Port Harcourt, capital of Rivers State, Nigeria, four crew members of a container ship were kidnapped. After the pirates escaped, the remaining crew was able to sail the ship to Senegal.