A 32-year-old man has died in hospital after an accident in which he is believed to have lost control of an off-road motorbike.
The man, who was from London, was taken to the Royal London Hospital after Thursday's accident in Park Avenue, Leysdown, on the Isle of Sheppey.
He died on Saturday morning from his injuries, Kent Police said.
A spokeswoman said the circumstances of the accident were unclear and the whereabouts of the bike were unknown.
She said emergency services were called to the scene by an onlooker but the 125cc bike had disappeared by the time they arrived.
"Our priority is to find it as soon as possible," said Pc Claire Russell-Thomas.
"The bike is a vital part of our inquiries and without it we can't piece together exactly what happened.
"We are also appealing for anyone who saw the incident, or events leading up to it, to phone us.
"It was a busy summer evening and we feel sure that someone must have seen what happened."