Offices at the Daily Mail were evacuated after a "suspicious package" was delivered to the newspaper's offices.
Staff at the Daily Mail and Metro in Northcliffe House in Kensington, west London were told to leave their desks at around lunchtime on Monday.
But police confirmed that the evacuation was a false alarm and said no arrests had been made.
"Officers have established that the item found in Derry Street, W8 is non-suspicious. No arrests made," said Kensington and Chelsea police.
Baz Bamigboye, the newspaper's entertainment columnist, tweeted: "Staff told to leave editorial floor as police test mysterious 'white powder' sent in post."
Police were in attendance at the building after the discovery of a "suspicious package", a spokesperson for the Metropolitan Police told The Independent.
Staff remained in the lobby and some were seen leaving the building, which also houses the Evening Standard, London Live, The Independent and i.
A number of Daily Mail staff said they had not yet been briefed on the situation and one said "rumours are flying".
"Staff flee to... pub" wrote Mr Bamigboye on Twitter.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies