Forensic investigators and police search teams scoured a street after a teenager was reportedly stabbed.
Officers said the attack took place at about 16:00 BST on Friday in Ardwick, Manchester, and left the victim with “serious injuries”.
Pictures from around the police cordon showed officers looking into a drain and carrying out fingertip searches.
The investigation appeared to also focus on a discarded bicycle, which was wrapped in plastic and taken away for examination. No arrests have been made so far.