A man has been arrested on suspicion of causing death by dangerous driving, after a three-year-old girl died in hospital following a collision.
The child was allegedly struck by a Mazda sports car on Kneesworth Street, Royston, Hertfordshire, shortly after 1500 BST on Sunday.
A five-year-old girl also involved in the collision was unhurt, police said. A man in his 60s is being questioned.
The three-year-old was confirmed dead at Addenbrooke's Hospital in Cambridge.
Insp Matt Thompson said: "This is a tragic incident. We are very keen to hear from anyone who saw the road traffic collision and so may be able to explain how it happened.
"This is quite a busy road, with the White Bear pub nearby, and people may have seen the collision take place while they were out and about.
"They could have been outside the pub at one of the tables or inside looking out of the window and seen something."