It happened on the Shore Road on Saturday night just after 2100 (BST).
Part of the road was closed between Fortwilliam Park and Skegoneill Ave.
The alert is now over and the Shore Road has been reopened. A local resident said something had exploded in a bin in an alleyway at York Parade.
Residents said the bang was so loud that their windows shook.
Police say the discovery of a large firework was behind a security alert in north Belfast.