The Australian Embassy in Washington says it is looking into Australian media reports that customs officials were checking people for the salty brown spread, a breakfast time favourite for generations of Aussies.
The US Food and Drug Administration has long prohibited imports of Vegemite because it contains folate, a B vitamin approved as an additive for just a few foods, including breakfast cereals.
But until recently there was no difficulty bringing in a few jars for personal use, satisfying many of the almost 100 thousand Australians and New Zealanders living in the US.
Like a similar British spread called Marmite, it usually goes on toast with butter or cheese, but is much more popular in Australia than Marmite is in Britain.
"Vegemite made me the man I am today," said Brad Blanks, a reporter with a New York breakfast radio show.
“In Australia the slogan is that Vegemite puts a rose in every cheek; but today America has slapped the cheek of every Australian."
Weekend reports from Australian and New Zealand media said some people had been searched or asked by US Customs and Border Protection agents if they were carrying Vegemite.
Agency officials were not immediately available for comment.
"From our perspective there is no food safety issue with Vegemite and we had been advised recently by US authorities that Vegemite was not of concern to them," an Australian embassy spokeswoman said.
Vegemite is made in Australia by US-based Kraft Foods.