A 16-year-old girl is thought to be in London after going missing from her New York home.
Victoria Grabowski has been missing since Saturday, and may have been "lured to London" by an older man she met online, her family told the BBC.
It is believed she took a flight from New York's JFK airport on Delta Air Line, arriving in London on Sunday.
The New York Police Department (NYPD) confirmed it was working "with London authorities to locate her whereabouts".
The police department said Ms Grabowski left home with "cash and extra clothing".
She is described as 5'3 (160 cm) tall, weighing 110 lbs (50 kilos).
The dual national travelled on her polish passport, her family said.
Delta Air Line policy allows anyone over 15 to fly internationally without a parent.