Four people suspected of creating an illegal landfill and poisoning the soil, have been detained by Beijing police, the city's Public Security Bureau reported on Thursday.

The bureau said in a statement that the four suspects were placed under criminal detention by Chaoyang district police on July 7, adding that further investigation is still ongoing.

In a previous investigation, the police found that one of the suspects, a 42-year-old surnamed Xue, had worked with three others to operate an illegal landfill in the district by occupying land and setting up private enclosures under the guise of requiring space to park construction machinery and equipment.

"Illegal dumping and landfills can poison the soil, and also seriously endangers food security," the police said in the statement.

They pledged to crack down on crimes related to the environment and natural resources to maintain the green development of the capital and support its growth by protecting the environment.