Gibraltar authorities have insisted an oil spill from a stranded cargo ship is "under control" after a collision.
Heavy fuel oil leaked from the bulk carrier OS 35, which has been stranded after it collided with an LNG tanker near the Bay of Gibraltar on the southern tip of Spain on Monday.
While authorities say it was a small amount of oil and the captain of Gibraltar Port has insisted that the leak is "fully under control", the environmental impact of the spill was not immediately clear.
Authorities announced that one person was arrested on Thursday in connection with the incident but gave no further information.
Divers sent to the ship have sealed the source of the leak - two vents in the fuel tanks, local authorities said.
The Gibraltar Port Authority said a small amount of oil escaped the perimeter of a boom placed to contain any spill. To prevent further expansion, a second barrier was planned to be deployed on Thursday.
Chief Minister of Gibraltar, Fabian Picardo, told Spanish broadcaster TVE earlier in the day that the operation to remove around 500 tonnes of the fuel from the ship's tanks should take around 50 hours using the vessel's own pumps.
The port authority is working with a Spanish marine rescue crew to collect a small amount of fuel oil, as well as to skim the fuel that has remained inside the boom.
The LNG tanker was not significantly affected by the collision, according to authorities.