Gibraltar said Friday that some heavy fuel continues to seep from a damaged and partly sunken bulk carrier ship off its shore.

The government said that despite Thursday’s sealing efforts to halt a slick, small amounts were still leaking on Friday.

In a statement, the government said there were reports of small numbers of oil-covered birds but that it was “taking every possible measure both on land and at sea to minimise the environmental impact of the spill.”

Crews have now begun extracting some 180 tons of sulphur fuel still on board after extracting most of the ship’s diesel, it said.

Meanwhile, the mayor of Spain’s southern town of La Linea de la Concepcion said some oil reached a nearby beach but clarified that it was lubricant from a leak when the ship collided with another vessel on Monday and not from Thursday’s fuel slick.

Mayor Juan Franco said the lubricant’s arrival was worrying “but it is not a tragedy”.

The environmental impact or the quantity of oil spilled on Thursday was not immediately clear.

The affected beach near La Linea was closed, as were three bathing areas in Gibraltar.

Gibraltar said the ship had been carrying 250 tons of diesel and still had 183 tons of fuel oil and 27 tons of lubricant oil in its tanks.

The 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.

The ship was ordered grounded in the shallows after colliding Monday with another vessel in the bay of Gibraltar.

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

The 584ft, 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.