Part of the promenade at Marsascala Bay collapsed early on Tuesday.
No one was injured but the council urged people to avoid the site, which is close to the parish church, along the seafront.
The collapsed area was raised, to allow rainwater runoff into the sea.
Mayor Mario Calleja said repair works by Infrastructure Malta will start on Wednesday morning.
The collapse happened during the night for unknown reasons, although a Facebook commenter said she had seen a cherry picker truck there.
A Times of Malta reader also confirmed the presence of the cherry picker saying volunteers were using it to prepare poles for festa decorations.