Valero says it is making good progress in repairing the major pipeline between its Pembroke refinery and its terminals at Kingsbury, Warwickshire, and in Manchester, and it has managed to maintain fuel supplies to its customers.

In a statement it said: “Following the breach of Mainline Pipeline on 4th October near Nantycaws, Carmarthenshire, Valero has continued to deploy significant resources around the clock to deal with this incident and made extremely good progress.”

Repairing the fractured pipeline involved closing the main A48 road over the weekend of October 14-17, and it added: “Our repair teams worked incredibly hard throughout the weekend, in very wet conditions, but completed the work to re-lay the pipeline across the A48, 12 hours ahead of schedule, re-opening the westbound carriageway at 7pm on Sunday evening. There is still some work required to fully reconnect the pipeline on either side and therefore the eastbound carriageway is due to remain closed for a little while longer.

“We made alternative plans to source product so that our customers could continue to be supplied with fuel, and apart from a few short-term delivery delays, due to increased delivery distances, our Texaco-branded service stations have been supplied in a timely manner throughout the incident.

“We continue to work with Natural Resources Wales to minimise the risk to the environment and to keep the impact on the wildlife to a minimum. Testing in the surrounding area to ensure there is no migration of oil to other sites is ongoing.

“We would again like to apologise to all local residents and commuters for the inconvenience this incident may have caused and to reassure them that we are working hard to resolve the issue as quickly as possible.”

In a letter to members of the Welsh Assembly rural affairs secretary Lesley Griffiths said it was estimated that around 140,000 litres of kerosene had leaked from the pipe.