(Bloomberg) -- A Singapore-registered oil tanker is missing after it was boarded earlier this week off the coast of Africa in what authorities are calling an act of piracy.

Owners of Success 9 have been unable to contact the ship since it was boarded Monday night off Ivory Coast, according to a statement from the government of Singapore, where the vessel is registered. The incident is being treated as an act of piracy, according to General Boniface Konan, director of the maritime security center for West Africa, known as Cresmao.

The ship, built 20 years ago, has the capacity to carry about 40,000 barrels of oil products or chemicals, according to data compiled by Bloomberg. About 20 crew members of various nationalities were on board when the pirates invaded it. 

The vessel was last seen off Ivory Coast on April 10, according to Bloomberg tanker tracking.

Piracy incidents fell to the lowest level in three decades during the first quarter of this year, according to the International Maritime Bureau, with 27 recorded incidents and just one successful hijacking and two attempts.

(Updates with ship tracking data in fourth paragraph. Previous version corrected name of security center director.)

©2023 Bloomberg L.P.