An envelope containing white powder caused public broadcaster Swedish Television to shut down a local newsroom on Wednesday.

Police cordoned off the area after a reporter opened mail containing an unidentified powder, daily newspaper Dagens Nyheter reported.

"When she opened the envelope it contained a white powder and we called the police immediately," news editor Martin Hult told Swedish Television.

Police later confirmed the powder wasn't dangerous but needs further testing.

Swedish Television said it had received several other threats after publishing an article on Monday about the leader of the anti-immigrant Sweden Democrats, Jimmie Akesson, hosting a summer party where Ultima Thule, a rock group associated with the country's extreme-right, had played. Enditem