4:27 PM PT -- Mel B and her lawyers went to the storage locker which they believe contained the boxes with sex tapes and Spice Girls memorabilia, but nothing was there and they left empty-handed.

Mel B made a beeline for the police station Tuesday after the folks at Public Storage refused to let her in a unit she believes contains her sex tapes and Spice Girls memorabilia.

The singer showed up at the Hollywood Police Station after getting a restraining order against her former nanny, Lorraine Gilles. Mel B claims Gilles -- whom she says estranged husband, Stephen Belafonte, got pregnant -- has a storage locker with 12 to 15 boxes of Mel B's stuff. Mel B believes the sex tapes are there and claims Gilles and Belafonte have extorted her, threatening to release them.

We're told for some reason Public Storage would not allow Mel B and her lawyers to enter the unit, so they went to the cops for help.