SA officials monitor NSW blackwater fish kill

SA officials are watching for any blackwater flowing into the state, after a major fishkill in NSW. (Samara Anderson/AAP PHOTOS) (AAP)

South Australian officials are monitoring a major fish kill in the Darling River in NSW amid concerns the event could spread across the border.

Millions of native fish, mostly Bony Herring, have washed up dead at Menindee and downstream towards Pooncarie, in the far west of NSW since late last month, as floodwaters receded and the region was hit by repeated heatwaves.