An investigation was launched after dramatic pictures of pollution in the River Ouzel were revealed.
Residents had taken to social media to raise concerns after a bright red streak had seeped into the river near Parsons Close recreation ground last week.
Laura Bree from Linslade, who regularly walks in the area, said she was shocked at some of the suspected pollution in the river.
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"I'm pretty upset about it," she said. "I assume its some sort of pollution we wouldn't want to see in the river. That streak of red in the river does not look right. I'm concerned about it affecting the wildlife and the water systems.
"I'm hoping the Environment Agency can investigate. These are not dumping grounds, our rivers are important for biodiversity."
An Environment Agency spokesperson said: “Our officers investigated a spill of coloured dye granules in the yard of a concrete manufacturer in Leighton Buzzard.
“The company swept up the granules, but rain later washed some of the residual dye into surface water drains running into the River Ouzel.
“Officers carried out tests of the river water and found there was no detrimental effect on its quality or risk to wildlife.
“Following our advice the company has now put measures in place to prevent similar incidents happening in the future.
“If members of the public suspect pollution they can call our 24-hour free incident hotline on 0800 80 70 60.”