A boy of 15 has been arrested on suspicion of attempted murder after three teenagers were hurt in a machete attack in a car park.
A 17-year-old boy suffered a serious knife wound to his chest and has undergone surgery following the disorder in Solihull on Wednesday.
Two others aged 17 and 18 suffered minor injuries and have been discharged.
Police were called to Marston Green Recreation Ground at 16:50 BST.
A statement said the force had "received reports that a group of teenagers were attacking each other with machetes".
The arrested boy has been released under investigation while inquiries continue.