Ukrainian police officers were questioning passers-by on Thursday (October 1), at the scene in Kyiv where a U.S. embassy worker was found unconscious with a head injury on Wednesday (September 30).
Ukrainian authorities said an American woman died in a hospital after a suspected assault in a park.
She was found by railway tracks next to a wooded area.
A search is underway to find the possible perpetrator.
Police said they're looking for a man with dark hair aged between 30 and 40.
He was wearing dark shorts and a t-shirt, and may have been involved.
The U.S. embassy said it was working with Ukrainian authorities to work out what happened.
Neither the woman's identity nor her job at the embassy have been revealed.