BANGKOK - Thai police said Monday they were seeking two Americans after the body parts of several babies - probably stolen from a medical museum - were found in five parcels destined for the US.

The two men, aged 31 and 33, crossed into neighbouring Cambodia on Sunday soon after the gruesome discovery of a baby's head, at least one foot and sheets of skin, during a routine scan of packages at a DHL package depot in Bangkok.

The parts, some of which were packed in a parcel marked "antique train set collection", were found in containers filled with formaldehyde solution, very similar to those used to preserve corpses at Bangkok's Siriraj Medical Museum.

The packages were addressed to Las Vegas, Nevada, prompting Thai police to ask the FBI for help to check the destination, deputy national police chief Ruangsak Jritake told reporters. "The initial assumption is that the body parts were probably stolen... as the hospital said some items were missing from an exhibition room," he added.

The deputy police chief said the boxes contained a left foot, skull, face and heart of babies as well as pieces of skin tattooed with Khmer letters and tiger patterns.

Security camera footage appeared to capture "foreign men" around the time the parts went missing, he said. Local media said the men were initially interviewed on Sunday but released after insisting they bought the body parts from a street market.

Police have asked the two foreign men to come back "for further investigation" over breaching customs laws, Ruangsak added.