A Facebook Marketplace deal has ended in an Auckland woman's arrest - accused of robbery - and seizure of firearm

Police say a victim met a woman at Westgate just after 1am overnight, to carry out a purchase.

Their phone and ATM card were allegedly stolen, and used to withdraw cash.

Police tracked and stopped a vehicle in Manurewa, finding a modified pistol, ammunition, cannabis and stolen property.

A 25-year-old woman's due in Waitakere District Court charged with theft and possession.