Sri Lanka says it is shipping 21 containers of waste back to Britain.
Officials said hazardous waste materials, including hospital waste, were found in some of the containers, in violation of international laws and European Union regulations.
Officials said the containers were supposed to be holding used mattresses, rugs and carpets for possible recycling.
An AFP reports says the containers arrived in Sri Lanka between September 2017 and March 2018.
The containers left Sri Lanka bound for Britain Saturday, officials said.
Several Asian countries have said they are tired of being the garbage dump for wealthy nations and have refused docking privileges to ships transporting waste.