According to Laing O'Rourke, the contractors who are building the 122m-tall mixed-use tower in Holloway Circus, the plates were ripped off by 'exceptionally high winds'.
The Health and Safety Executive is now investigating the cause of the accident, which led to the evacuation of nearby shops and offices. Fortunately no one was hurt.
It is the second time the emergency services have been called in to close streets at the base of the skyscraper after reports of falling material. Back in February a piece of scaffolding plummeted nearly 120m, only just missing passing cars and construction workers.
A spokesman for Laing O'Rourke admitted the incident was 'unacceptable'. He said: '[We] would like to express our apologies to everyone who is inconvenienced.
'Five pieces of metal cladding became unstable in the exceptionally high winds which affected other properties in Birmingham.
'Laing O'Rourke has begun an immediate investigation to understand what happened and why.'
He added: 'Incidents of this nature are unacceptable.'
Once complete, the £70 million tower will become Birmingham's tallest building and will house 150 apartments and a 220-bedroom, four-star hotel.