(Adds Gap statement.)

LONDON (AFP)--A factory that produces jeans for U.S. clothing retailers Gap Inc. (GPS) and Levi Strauss & Co. is illegally dumping chemical waste in Lesotho, posing a major hazard to children, the Sunday Times reports.

The weekly paper said it had discovered that the plant, operated by Taiwanese firm Nien Hsing Textile Co. Ltd. (1451.TW), was pouring dark blue effluent into a river used for cooking and bathing.

The paper also alleged that the firm was dumping needles, razors and harmful chemicals at two municipal dumps that attract young children who search for pieces of clothing to sell.

Many of the children worked up to 10 hours a day and complained of ailments that included breathing difficulties, weeping eyes and skin rashes, the Sunday Times reports.

Both Gap and Levi Strauss have ordered immediate investigations, it said.

Levi Strauss said it was "disturbed" by the findings, while Gap said in a separate statement that it has put the factory on notice to improve.

"As soon as we were alerted of these issues, we immediately investigated the situation on the ground in Lesotho, commissioned an independent monitoring organization to conduct its own investigation, and placed one of the factories involved on immediate notice until our investigation is complete," said Dan Henkle, Gap's senior vice president of global responsibility.

"Our primary focus, however, continues to be on the workers and their community," added Henkle in the statement.

"In keeping with our strong and transparent history on any sourcing issues, we will continue to act swiftly, decisively and thoughtfully in doing everything possible to protect the workers at the factories that make our products and the communities in which they live and work."