The stage collapse at Ottawa's Bluesfest after a July 2011 windstorm was caused by weather and a lack of preparation, according to a report from Ontario's Ministry of Labour.

Workers cut ties on wind screens of the main stage during the July 2011 storm at Ottawa's Bluesfest. (Submitted by Adam Dietrich)

The engineer who analyzed the stage, which collapsed during a Cheap Trick concert on July 17, 2011, said workers should have removed the wind flaps at the side and back of the stage before the storm.

That way, the structure would have been able to withstand the wind, which was recorded at 96 km/h at the Ottawa airport that evening, the report said.

The engineer also said it was caused partly by a "severe weather event."

In his report, Ministry of Labour investigator Jason Gordon repeatedly said Groupe Berger "failed as an employer" under the Occupational Health and Safety Act.

The engineer who analyzed the stage said the company should have released the wind flaps after Environment Canada forecast storms and damaging winds more than an hour before the collapse.

Groupe Berger also failed to notify stagehands of a change in procedure related to how they release the wind flaps, the engineer wrote in May 2012, as stage hands were unable to cut or release cable ties before the collapse.

Ministry of Labour spokesman Matt Blajer told CBC News in July no charges would be laid in connection with the stage collapse because the evidence gathered "did not meet the legal threshold for charges" under Ontario's Occupational Health and Safety Act.

Three people were injured in the stage collapse, including a Cheap Trick employee who suffered abdomen, pelvis and upper leg injuries. All three people were soon released from hospital.

0- Investigation Report