Officers from Natural Resources Wales (NRW) are investigating a river pollution incident in Ceredigion.
It is thought that effluent from an anaerobic digestion (AD) plant was released into a stream in the Lampeter area.
This has flowed into the Afon Dulas which enters the Teifi in Lampeter.
High river levels mean that it is not possible to contain much of the pollution. But this might also help to dilute the pollution and reduce the damage it might cause.
In the meantime, NRW officers are working with the site operator to clear some of the remaining effluent from the site yard and they will continue to work to minimise any further pollution.
There is no indication at this point about the extent of the impact, NRW says.
NRW officers confirm however that there is no connection between the source of the pollution and an incident on the Teifi in December.
Ben Wilson, Ceredigion Operations Manager for Natural Resources Wales, said: “We’ve been able to confirm that the pollution has been stopped at source, but a large amount of this material had already gone in to the river.
“Our officers remain on site working with the operator to minimise the risk of further pollution.”