OSHA found all four contractors involved in the car park project to have breached health and safety regulations. Of the nine health and safety violations discovered, six were by concrete sub-contractor Fabi Construction.
OSHA said the most serious charge levelled at Fabi was that the company showed an 'intentional disregard of the requirements of the Occupational Safety & Health Act.'
The penalty for this offence is a $70,000 (£39,000) fine.
Main contractor Keating Building Corporation, reinforcement contractor Mitchell Bar Placement, and reinforcement checking engineer Site Blauvelt Engineers were each found guilty of a single breach of safety regulations. Each was fined $7,000 (£3,900).
A spokesman for contractor Keating confirmed that it would appeal against the decision. 'While we understand OSHA's position we feel there is still much information to be gathered and analysed, ' he said. 'It is our intention to appeal this specific citation as we continue that important process.'
He added: 'There is nothing in OHSA's findings or in our own investigation that points in any way to a direct and clear-cut cause of this tragedy. There are no simple answers here.'
Client Tropicana Casino also declined to comment on OHSA's findings and refused to say what its plans were for future development of the collapse site.