A civil engineer has concluded that the balcony collapse that killed six people and injured seven others Tuesday was not caused by the structural planning of the building and could instead be due to the building’s waterproofing system.

Gene St. Onge, the founder and principal of the civil and structural engineering firm St. Onge & Associates, carried out an independent investigation of the structural design of the Library Gardens apartment complex. He found no evidence that the building’s structural design violated the city’s building code and believed that the building was designed properly.

St. Onge said the problem may have instead been the result of a faulty waterproofing system, which would have allowed water to seep in and damage the wooden structure of the balcony, causing dry rot. St. Onge, however, said he is not an expert on waterproofing systems and therefore could not make any definitive judgments on the matter.

St. Onge added that “if it was not for the dry rot, the balcony should have easily supported 13 people,” the number reportedly on the balcony at the time of the collapse.

Other experts who have independently examined the balcony collapse have said the balcony appeared to suffer from dry rot.

Publicly released city documents also show an apparent history of dry rotting in the apartment complex. The city found in an inspection on September 11, 2013 that the “floor deck is dry rotted” in an apartment room and in the building’s common area. Another inspection on December 20, 2013 found that the problem has been fixed and a certificate of compliance was issued to the building by the city in January.

There is no timetable yet for the conclusion of the city’s investigation into the collapse and the release of its report, according to city spokesperson Matthai Chakko.

The building’s fourth-floor balcony, which was directly below the balcony that fell, was removed Wednesday after the city deemed it to be structurally unsafe.

Two of those injured in the collapse are being treated at John Muir Hospital and, as of Friday, were said to be in fair condition. Two other hospitals could not be reached to give updates on the conditions of the other victims.

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