A Japanese unmanned cargo ship plunged into the atmosphere over the South Pacific early Wednesday after completing a supply mission to the International Space Station (ISS), the Japanese space agency said.

The Kounotori 5 was loaded with 4.6 tons of waste and observational equipment when it separated from the space station Tuesday. Most of the ship is presumed to have burned up in reentry though some parts may have plunged into the southern Pacific.

The Japan Aerospace Exploration Agency's Mayumi Matsuura, who served as flight director of the cargo ship, told reporters that she was happy the vehicle performed its mission.

The Kounotori 5 arrived at the ISS on Aug. 24, carrying about 5.5 tons of supplies and equipment to conduct experiments. Japanese astronaut Kimiya Yui, who is staying on the ISS, undocked the cargo ship early Tuesday.

Japan's successful unmanned cargo delivery came after similar missions by other countries failed.