St. Louis police say an Uber driver robbed a customer by using a translator app to demand cash.
A 28-year-old man was not injured after giving the driver money.
Police say the man left his phone in the Uber and arranged to meet the driver early Sunday to retrieve it.
The St. Louis Post-Dispatch reports when they met, the driver displayed a pocket knife and used the app to demand cash. The apps are used to communicate with someone in another language on a mobile device.
The driver, a 41-year-old man, drove away and as of Monday officers hadn't located him yet.