Cruise ships may have served thousands of vacationers carcinogen-laced drinking water over the past seven years, according to a damning new report.

A paint capable of leaching acrylonitrile, a tumor-causing toxin, was used to paint the water tanks of up to 50 cruise liners owned by cruise companies including Royal Caribbean, Norwegian Cruise Line, and others in 2004, a Sunday Times of London report reveals.

The paint was made by the Danish company Hempel, which was able to keep the cancer scare under wraps due to a gag order a court issued against whistleblower Brian Bradford, a paint inspector charged with keeping tabs on the repainting of tanks on two Norwegian cruise ships.

A spokeswoman for Norwegian Cruise Line told the New York Post that The drinking water on Norwegian Star and Norwegian Dawn has always been and remains safe.

Bradord allegedly discovered black residue in the tanks, informed Norwegian, and was subsequently fired by Hempel, according to the report.