Cyanide letter contained threat against Tiger Woods

Police say the US Embassy in New Zealand received a letter containing cyanide and threats to disrupt the New Zealand Open.

Assistant police commissioner Jon White says the letter made clear the threats were made because "Tiger Woods, the world's Number one golfer, was playing."

He says a "small" amount of cyanide was sent in the letter which was received by the embassy in Wellington in December.

"The threatening letter was sent to the US embassy and Israelis were also mentioned in it," said White.

"We're talking and working with the diplomatic community and giving them much the same sort of advice as we are the public generally."

Police have warned spectators attending the New Zealand Open, which begins Thursday at Paraparaumu Beach to be vigilant, particularly with food.

Catering staff have been warned of the possibility of attempts to contaminate food provided to the players and public.

The US embassy in Wellington released a statement confirming that cyanide was received and that the letter was immediately passed on to police.

"We are confident that appropriate steps are being taken. In the interests of security and not wanting to prejudice the investigation in any way, we are unable to comment further," said the statement.

Tournament organisers announced last May that Woods would make his first appearance in New Zealand. Woods' caddie, Steve Williams, grew up around the Paraparaumu course.