Northumbria Police is investigating the attack on the landmark, beside Hadrian’s Wall in Northumberland, and said the teenager had been released.
Two men in their 30s and a man in his 60s were arrested on suspicion of criminal damage and are on police bail.
A case of vandalism
Police said the tree was ‘deliberately’ felled overnight on 27-28 September.
Det Ch Insp Rebecca Fenney-Menzies said the force was ‘committed to establishing the full circumstances’ and bringing ‘any offenders to justice’.
‘We completely recognise the feeling of loss in the community and further afield following the deliberate felling of [the Sycamore Gap tree],’ she said.
Repair-plans in the book
She asked members of the public to continue coming forward with information, since this ‘could prove vital’ to police inquiries.
Earlier this month, experts said they were looking at repair options after they found part of Hadrian’s Wall had suffered damage where the tree was felled.