MADRID (AP) — The mayor of a southern town in Spain said Friday that an oil slick from a damaged and partly sunken bulk carrier ship off Gibraltar has reached a nearby Spanish beach.

La Línea de la Concepción Mayor Juan Franco said fuel from the leakage had been pushed by winds and currents to the beach.

The leakage occurred Thursday but divers sealed the source. The environmental impact or the quantity of oil spilled was not immediately clear.

“What has entered is a worrying spillage but it is not a tragedy,” Franco said. He said the most important issue was to remove the remaining fuel oil on the tanker safely.

Gibraltar officials said early Friday that 80% of the diesel on the ship had been removed but that some 180 tons of heavy fuel are still on board. The ship was ordered grounded in the shallows after colliding Monday with another vessel in the bay of the British territory located at the western entrance to the Mediterranean Sea.

A government spokesman said there had been no further seepage of heavy fuel since Thursday and that the situation was under control.

The spokesman, who was not authorized to be named publicly, said the ship had been carrying 250 tons of diesel and still had 183 tons of heavy fuel oil and 27 tons of lubricant oil in its tanks.

The heavy fuel oil is potentially more damaging to the environment and more difficult to extract, raising concerns in Spain and Gibraltar for marine life and tourism in the area.

Fabian Picardo, the head of Gibraltar’s government, told Spain’s Cadena SER radio that work would begin on removing the heavy fuel after the diesel is fully extracted.

The usually busy port of Gibraltar remains closed, but the neighboring Algeciras port in Spain is fully operational.

The 178-meter (584-foot), Tuvalu-registered OS 35 was carrying a cargo of steel bars. The LNG carrier with which it collided sustained little damage. No one was injured in the collision.

The captain of the damaged ship has been detained for allegedly not obeying Gibraltar port orders initially after the collision.