The source of a leak which led to an unknown amount of "thick, heavy oil" spilling into a Pembrokeshire estuary has been contained, officials said.
It happened at a jetty on the Milford Haven waterway - by the Valero refinery - at about midnight on Wednesday.
It is understood the leak came from pipework and booms have been placed in the water to stop the oil spreading.
But Milford Haven harbourmaster Mike Ryan said a small amount had reached shore. Valero has apologised.
The company said an operation was under way to respond to the spill and it had "activated its contingency response plans".
A statement added: "Valero would like to take this opportunity to apologise to all local residents for any inconvenience this incident may have caused and to reassure them that we are working hard to resolve the issue as quickly as possible."
Pembrokeshire council said it was hoped the oil would be collected "over the next day or two" and Cristoffer Tomos, the authority's cabinet member for environment, said the leak was understood to have come from pipework.
Shipping was halted while the spill was evaluated, but the route has since reopened.
The spillage was initially reported by Valero which told the Port of Milford Haven a "petroleum product" had been released.
Harbourmaster Mr Ryan said the source had been contained and he was expecting an update from Valero on Friday about how much oil went into the water.
"There is oil coming ashore and I suspect that will continue for the next few days," he said.
"We've had reports later on this afternoon of oil globules of smaller sizes coming ashore at Dale and we're working to put plans in place to recover them tomorrow morning."
He added: "We'll see oil emerge in various places and we are primed and ready with our multi-agency colleagues to tackle that situation as and when it arises."
Andrea Winterton, from Natural Resources Wales, said: "Our officers have been working with Milford Haven Port Authority, and other organisations, taking action to reduce the impact of an oil spill in the waterway."
She added beach surveys were being carried out and booms were being used to protect the salt marshes around Sandy Haven and the Gann estuary.
The public - particularly dog owners - has been urged to watch out for pollution on the coastline.