The carrier — the OS 35 — has been beached in the Bay of Gibraltar since the two vessels collided late on Monday off the territory located on the southern tip of the Iberian peninsula.
No one was injured in the accident. The 24 crew members of the carrier were evacuated.
A boom — a temporary floating barrier used to contain an oil spill — had been placed in the area of the collision.
“The Gibraltar Port Authority has confirmed a leak of heavy fuel oil a small amount of which has escaped the perimeter of the boom,” the government of Gibraltar said in a statement.
In a separate statement, it added the leak “is fully under control”.
“The priority is to corral and collect the free floating oil that has escaped the boom, as well as to remove the oil that has remained contained inside the boom,” it added.
Bulk carriers are vessels dedicated to transporting solid goods, such as grain, and the fuel on board is that used by the ship itself.
The collision happened when the OS 35 was moving to exit the Bay of Gibraltar. The liquefied natural gas tanker suffered no significant damage.
Gibraltar’s busy port has been mostly closed since the accident.
The territory, measuring just 6.8 square kilometres (2.6 square miles), overlooks the only entrance to the Mediterranean from the Atlantic Ocean, putting it on the shipping route to the Middle East via the Suez Canal.