Police deployed officers and staff to check nearby public places, tourist attractions and hotels. Details of the boys were circulated to public transport operators and Solent ferry companies.
An address given for the family on the Isle of Wight was checked by officers. The details provided were found to be incorrect.
The force is keeping an open mind about the circumstances of this report. There is no evidence at this time to confirm a criminal offence has been committed deliberately. There could be a completely innocent explanation for what happened.
We are renewing an appeal for the parents or any relatives of these two boys to contact the police."
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A man's been treated in hospital after being hit by a police car responding to an emergency call in Brighton. It happened on Kings Road.