Andy Weston-Webb, president of MasterFoods Australia New Zealand, said a threat had been made to poison a member of the public using the chocolate bars.
Tens of thousands of bars would be recalled, Weston-Webb said. "No one should eat a Mars or Snickers bar that they've bought. Please destroy it," he told reporters. "It's not safe to eat Mars or Snickers bars."
"Due to the very serious nature of the tampering threats, we are instigating an immediate withdrawal of Snickers and Mars from all New South Wales (state) retail outlets," Weston-Webb said in a statement.
However, he said, "At this stage the withdrawal is precautionary, as there is no evidence of anyone having become ill as a result of the threat."
Media reported that the culprit, who remains at large, had sent threatening letters and a Snickers bar to MasterFoods, which makes the popular bars in Australia.
Police said the Snickers appeared to have been contaminated with a substance that has yet to be identified.
"The letters do not contain any demands for money. However the author directs a series of complaints to a third party," New South Wales police said in a statement. They did not identify the third party.
Police said the letters claim seven Snickers and Mars bars were poisoned.
Detectives have formed a special team to track down the person who sent the threat, while MasterFoods set up a special consumer telephone hot line for people seeking details of the threat.
