Thai police say two Americans have left the country after trying to smuggle out body parts, including a baby's head.
The men were freed after questioning on Saturday over three parcels containing human remains bound for the US.
Police said that staff at a DHL depot in Bangkok were doing a routine check on several parcels labelled as toys when they made the discovery.
The men told officers they bought the items at a night market and wanted to give them to friends as a joke.
Police named one of the Americans as a controversial video maker, Ryan McPherson.
The BBC's Jonathan Head in Bangkok says he became notorious for making violent exploitative videos a decade ago about homeless men, and was questioned by police then.
Police in Bangkok say the parcels were bound for addresses in Las Vegas. One reportedly had a baby's head, a baby's foot sliced into three parts, an adult heart with a stab wound, and pieces of adult human skin with tattoos.
The items were in five plastic containers filled with preserving fluid, packed into three packages. DHL staff discovered them when putting the boxes through an X-ray machine.
Police said the body parts appeared to have been removed and preserved by a medical professional.
AFP news agency said the containers looked similar to those used to preserve corpses at Bangkok's Siriraj Medical Museum.
Speaking at a news conference, deputy national police chief Ruangsak Jritake said: "We have received information that shows they were stolen from one of the big hospitals that is located in the Thonburi area. It is a famous hospital. But we are still looking for clearer evidence."
The Nation newspaper said one of the two men who tried to post the items was questioned by Thai police for four hours on Saturday night in the presence of US embassy officials, before he was released.
Police told reporters they released the men as they had no grounds to prosecute them. The two men have since left for Cambodia, police say, and the FBI in the US have been informed.
In 2012 a Briton was arrested in Bangkok for possession of six foetuses wrapped in gold leaf. Police had been tipped off that the foetuses were being sold through a website advertising black magic.