Police who found the three boys who went missing four days ago said there may have been a plan to "spirit them out of the country."
They failed to return to their foster carers' home in Sunderland, after setting out on a tea-time bike ride to a local park.
Instead, they caught a Metro to Newcastle, then took a pre-booked taxi to London and spent two nights in the capital before heading for Birmingham.
Superintendent Alan Veitch, who led the major investigation to find them, said it was "entirely possible" that the plan was to get the boys out of the country.
More top news
Aitor Karanka remains wary of Andy Carroll's aerial ability ahead of Middlesbrough's game against West Ham United
Michael Gilbert is accused of crashing his bus into a bank. He denies causing death by dangerous driving.
David Moyes admits Sunderland have missed striker Victor Anichebe who looks set for a return against his former club West Brom.