Five companies involved in the construction of the Berkeley apartment building, where six students died when a balcony collapsed last summer, face losing their license.

The five companies 'performed inferior work that led to the accident last year,' the California State Contractor's licensing board found after a nine month investigation.

A top official in the board said that 'poor workmanship' led to the water damage that caused the balcony to rot and eventually collapse.

Five Irish students from Ireland fell from a height of 50 feet when the balcony gave way in June 2015. Lorcan Miller, Eimear Walsh, Olivia Burke, Niccolai Schuster, and Eoghan Culligan, were all in the San Francisco Bay area on working visas when the tragedy occurred. They were all from south Dublin.

A sixth student, Ashley Donohue, who lived in California and was a cousin of Olivia Burke, also died.

The firms in question, were responsible for the framing, plastering and waterproofing work of the building. They also supplied ventilation equipment.

The families of those killed and injured in the incident, have since began legal proceedings for unspecified damages from dozens of companies, including the same five cited by the state board and the building's owner.

An administrative hearing will be held to determine if the companies should have their licenses revoked. California law allows the state to suspend or revoke the licenses of builders that knowingly depart from approved architectural plans or do substandard work, according to the board. 

The five companies are: general contractor Segue Construction, Etter and Sons Construction, North State Plastering, R. Brothers Waterproofing and The Energy Store of California in Sacramento.