Key Points:

There are no concerns for the safety of four Beehive staff after they were caught up in a white powder scare today.

Fire engines and ambulances raced to Parliament this morning after an envelope containing powder was opened in the office of the prime minister on the eighth floor of the Beehive.

Prime Minister Helen Clark's spokesman said three of her office staff and one security guard were examined after the incident.

The substance had not been identified, but the spokesman said no concerns were held for the staff's health and they had suffered no ill effects.

The eighth floor houses the Department of Prime Minister and Cabinet, and some of Miss Clark's office staff.

Miss Clark's personal office is on the ninth floor, but she was not there this morning.

The spokesman said the eighth floor had been evacuated and was being decontaminated.

One office remained sealed off.

No other floors were evacuated while fire engines and ambulances remained on the grounds of Parliament for about 90 minutes.

The spokesman said he had little information about the envelope and could not confirm it was addressed to the prime minister.

He also did know whether there was any message or identifying marks.

The incident today could cause some concerns about parliamentary security as all correspondence and packages sent to the complex are meant to be screened before they are delivered to offices.

Some Beehive staff told NZPA that they were upset by the incident and they had been told they could go home for the day if they wished.

In the wake of the September 2001 terrorist attacks there were a spate of anthrax scares around the United States and the world.

Many were hoaxes but in the US five people died and 17 were made ill.

The case resurfaced last week after the FBI said a US Army scientist, Dr Bruce Ivins, killed himself as he was about to be charged as the man behind the attacks.

They said the case against Dr Ivins stemmed from new scientific tests - as anthrax spores found in his office were linked to spores sent through the mail.

Dr Ivins was a microbiologist who worked on developing an anthrax vaccine.

The FBI have claimed he was motivated by his desire to receive funding for his work.

His family and friends say he was innocent and others have said they doubt the FBI's evidence against him.

There were a number of white powder scares in New Zealand in 2001 and 2002 as well.

This included one other incident in the Beehive when white powder was sent to former Alliance Cabinet minister Sandra Lee.

All of the scares in New Zealand proved to contain harmless substances.

More recently there have been a spate of parcels containing poison being sent to offices around New Zealand

Police are still investigating the source of at least 16 suspicious letters thought to contain 1080 poison sent to local authorities, central government and private businesses in Wellington and other centres.

Poisoned pellets have also been scattered on the steps of Parliament and fake pellets deposited in Christchurch's Hagley Park and Botanical Gardens.