Twenty-one containers full of rubbish and hazardous waste which the UK shipped to Sri Lanka are now on their way back.
They departed Sri Lanka on Saturday, bound for Britain.
The containers were supposed to contain used mattresses, carpeting and rugs destined for recycling, but were discovered to also contain hospital waste, plastic and polythene, officials said.
Customs did not reveal the type of hospital waste, but previous illegally imported containers had included rags, bandages and body parts from mortuaries, according to officials.
The 21 containers were part of a shipment of 242. The remaining 221 are abandoned at a free trade zone outside Colombo.
The UK Environment Agency said it was committed to tackling illegal waste exports.
A spokesman said, “We are in contact with the Sri Lankan authorities and have requested more information which would allow us to launch a formal investigation.”
In recent years, several Asian countries have reconsidered being the wealthy world’s rubbish dump.
Since China stopped importing foreign waste, countries such as Malaysia began to take up the slack by importing more, usually illegally.
But in January, Malaysia sent 42 containers of imported plastic waste back to the UK after disposing of it in illegal factories caused significant pollution problems and consequent protests.