The suspects entered Guarulhos airport in São Paulo dressed as police officers and took the gold, which had been destined for New York and Zurich.
Two airport workers were taken hostage, according to police.
Some reports suggested the suspects may have kidnapped the family of a senior employee on Wednesday to gain inside information about the cargo.
The suspects disguised their pickup truck as a Brazilian federal police vehicle and confronted workers, forcing them to move the gold into their vehicle.
According to security footage, four men left the vehicle and at least one had a rifle.
A spokesperson for the airport said that no one was hurt in the incident but did not comment reports of hostages.
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