Spierings, who returned from a trip to China today, said he was satisfied the situation there was stable after talks with the Chinese authorities.
"I decided very late last night that the situation was stable," Spierings told a news conference underway in Auckland.
"Like I said in China, I do apologise to the consumers and to the public for the anxiety and distress that this has caused," he said.
Asked if he would resign over the scare, Spierings said: "That's not up to me, it's up to the board.''
In answer to another question over the cause of the contamination, Spierings said: "We know what happened, but we do not know why it happened.''
He said an internal investigation had already started and an external investigation was also likely.
"It's likely the Government will call for that as well ... and we welcome that,'' he said.
Spierings said all contaminated stock had been contained and there was now `"little or no risk'' for consumers.
