Concerns have risen over large mountains of waste appearing in areas such as Evesham and Peopleton.
The Environment Agency says it is investigating at three sites over suspected illegal waste tipping.
Two sites in Peopleton and Evesham are also being investigated, the Environment Agency says.
One dump is affecting house prices, with owners saying estate agents' current advice is "don't sell".
Businesses were found responsible for unlawfully discarding wasted in Pershore and Peopleton.
