A man who went to police after finding white powder inside a greeting card he received triggered the evacuation of a Brisbane police station, after authorities feared the powder - later discovered to be cocaine - was anthrax.

Officers set up a 50-metre exclusion zone at Boondall Police Station on Monday evening, a Queensland Police Service spokesman said.

The recipient had spotted white powder in one of two greeting cards which were delivered by mail from the UK to an Aspley address earlier in the day.

He put the cards into a plastic bag and went to police, where he asked for help.

Police were forced to set up an exclusion zone while the Queensland Fire and Emergency Service conducted a dip-test on the powder.

Preliminary results suggested it was cocaine but it has been sent to the John Tonge Centre for scientific analysis.

Police are working with their UK counterparts to determine who sent the greeting cards.