BERLIN (AP) — German police say they've closed off a portion of a street in a southern city after a suspicious package was sent to a building.

Ulm police tweeted Wednesday that they are investigating the package but further information wasn't immediately available and their phone lines were busy.

Germany has been on edge after authorities last week said they were investigating a plot to extort money from delivery company DHL Express.

That announcement came after a package sent to a pharmacy in Potsdam containing wires, batteries and nails to resemble a bomb prompted the evacuation of a Christmas market on the same street.

The package contained a link to an online message threatening to send more packages unless DHL paid millions of euros (dollars).