Sri Lanka has sent 3,000 tonnes of rubbish to the UK.
A British company sent the waste to the South Asian island state between 2017 and 2019.
The 263 containers were then declared as used mattresses and carpets for recycling, a customs official in Colombo told reporters on Monday.
However, the containers gave off an unpleasant smell and when the officials looked, they found medical waste inside, including material from mortuaries.
A court ordered the return of all 263 containers in 2020.
The last of them were sent on Monday.
The authorities said it was still unclear why a company in Sri Lanka imported the incorrectly declared waste.
Investigations would still be ongoing.
Among other things, Sri Lanka imports mattresses, plastic and paper for recycling.
Environmental organizations in the country have urged their government to ensure that not much recyclable waste enters the country and is dumped illegally.