An envelope containing an unknown powder and addressed to Greens senator Sarah Hanson-Young has been sent to the party's South Australian state office.

Key points: A spokesperson for Senator Hanson-Young said a threat was made against her

A spokesperson for Senator Hanson-Young said a threat was made against her Police have not yet identified the substance contained in the envelope

Police have not yet identified the substance contained in the envelope No-one was injured when the envelope was opened this afternoon

Police were called to the office on Wright Street in Adelaide's CBD just after 4:00pm, after the envelope was opened.

A spokesperson for Ms Hanson-Young confirmed a threat had been made against the senator, and police were investigating.

The substance inside the envelope is yet to be identified, but the Metropolitan Fire Service is treating it as a HAZMAT (hazardous materials) incident.

"Emergency services are currently at Wright Street in the city after a suspicious package was found," police said in a statement.

"Patrols were called to the office of the Greens after a letter addressed to federal [MP] Sarah Hanson-Young was opened and found to contain a powder.

"No-one has been injured and further information will be provided as it comes to hand."

It is understood Senator Hanson-Young was not the one who opened the envelope.

The incident came only hours after she claimed victory in her re-election battle.

She secured a swing of nearly six per cent in Saturday's federal election.

"I've had three years of people telling me I couldn't do this," she said earlier today.

"Well, a bit of hard work, a bit of honesty, standing up to the bastards and here we are."

Police have asked anyone with information about the security scare to contact Crime Stoppers on 1800 333 000.