Greenpeace says its Sydney headquarters have been raided and shutdown by the Australian Federal Police (AFP) following last week's destruction of a trial wheat crop in Canberra.

Last Thursday Greenpeace activists scaled the fences of a CSIRO experimental farm at Ginninderra in the capital's north and destroyed a crop of genetically modified wheat with brush-cutters.

The crop was to be used in the first human trials in Australia.

Greenpeace says it took the dramatic action because of concerns over health, cross-contamination and the secrecy surrounding the experiments.

The CSIRO maintains the experiment, which did not introduce any new genes to the plants, was safe.

Greenpeace says the AFP raided its offices just before midday Thursday.

Police seized evidence as part of their investigation into allegations of trespassing and damaging property.

Greenpeace's head of campaigns, Steve Campbell, says no arrests were made.

"We cooperated with police and will continue to assist them in their investigation, but we will also also continue to work on our campaign to bring a spotlight on genetically modified wheat in Australia," he said.

"A couple of people did speak to the police yesterday and they've identified themselves to the police, but no arrests have been made at this stage."