Milford Haven oil spill estimated at 'up to 10,000 litres'
A "heavy" oil spill which prompted a major clean-up operation could be as much as 10,000 litres, port chiefs have said.
The Valero Jetty in Pembrokeshire, was closed off after the leak on Thursday.
Officials said the vast majority of the spill was contained - although more tests are under way.
Andrea Winterton, of Natural Resources Wales (NRW), said it was difficult to predict what the environmental impacts will be.
"We're not sure where or when any further oil will come ashore... but we'll keep monitoring all the beaches and working with our partners to ensure where it does come ashore, we clean it up appropriately," she said.
"The oil has stopped, the leak has stopped... until there's more that comes ashore, it's very difficult to say what's happened to it and what the environmental impacts are going to be."
The spillage was initially reported by the Valero refinery, with the firm now estimating that 7,500 to 10,000 litres (1,650 to 2,200 gallons) of "heavy fuel oil" leaked overnight between 2 and 3 January.
As a comparison, the average household bath holds 80 litres of water.
It is understood the leak came from pipework.
Habourmaster Mike Ryan said a "well-rehearsed" clean-up operation involved Natural Resources Wales, Pembrokeshire County Council, Maritime Coastguard Agency as well as Valero.
Floating devices called "booms" were used to contain most of the spillage and a drone has been used to see where the oil has spread.
Officials said oil has been seen on the shore at Dale and Musselwick Bay.
In the meantime, the boom devices will stay put until NRW is "confident the risk" to wildlife and sensitive salt marshes has passed.
The agency added a full investigation was under way.
Shipping was halted while the spill was evaluated, but the route has since reopened.
The public - particularly dog owners - has been urged to watch out for pollution on the coastline.
Wildlife charity RSPB Cymru said while the impact of the spill remained unclear, it still was "extremely worried" about the incident.
A spokeswoman added: "Any oil spill has the potential to seriously affect birds."