The body, with no identification, was left hanging halfway out of the plane for several hours until it was removed by police.
Police later said an autopsy would be carried out on the decomposing corpse.
But the Aviation Herald reported online that the blood smears had been noticed in Munich by a plane spotter who took a photograph.
It reports that ground staff at Munich Airport also noticed the blood stains, but took no action, putting it down to a bird strike.
The Aviation Herald quoted Western Global Airlines as saying: “During a routine fuel stop in Zimbabwe, a body was found in the lower compartment. It is presumed to be of a stowaway who may have entered the aircraft during a previous stop. The situation is under review.”
Aviation enthusiasts speculated online that it was likely the stowaway would have been able to get in from the outside but might have been crushed during gear retraction.
Late on Friday security officials surrounded the aircraft, which had been parked near the runway since it landed, and moved it to aircraft ground services where its interior was being dismantled.
This information, from insiders in aviation circles, has not yet been released to the public until now.
The US freighter crew, a captain, co-pilot, reserve pilot, engineer and loading officer were taken away and were understood to be staying, under guard, in a city centre hotel.
It is not clear whether they are still in Zimbabwe.
The Reserve Bank reiterated that the process of printing South African currency abroad, and transporting it, was part of currency operations and business contingency planning.
“To achieve this and ensure that contingency plans are robust and regularly tested, a small percentage of the Reserve Bank’s annual bank-note order is outsourced to credible and vetted international printing companies.
“The bulk of South African currency is produced at its wholly owned subsidiary, the South African Banknote Company,” it said.