Johannesburg - A section of a dental clinic at Johannesburg's Charlotte Maxeke Hospital has been cordoned off because part of a ceiling that collapsed in January has still not been repaired, according to two sources.Speaking on condition of anonymity after Thursday afternoon's ceiling collapse at the hospital entrance, staff said a section at the dental clinic had already collapsed in January.One worker said Gauteng Infrastructure MEC Jacob Mamabolo's statement that the rest of the building was safe, was false.A worker said that, when staff arrived at the dental clinic on January 23, they found a part of the ceiling had caved in. The clinic is run by the University of the Witwatersrand.Gauteng infrastructure department spokesperson Theo Nkonki could not immediately confirm the incident, but said Mamabolo was due back at the hospital on Friday to assess the situation.A section of the roof at the large hospital in Parktown, Johannesburg, collapsed around 14:30 on Thursday. Seven people were injured, three of them seriously, Johannesburg emergency services said.Shoddy workmanshipSpeaking at the site on Thursday, Mamabolo alleged that shoddy workmanship by contractors who were waterproofing the roof had played a role in the collapse."The way they were removing the concrete stone, we could see they did not do a proper check on the strength of the building or the roof itself."Mamabolo said the contractor had removed concrete stones and placed them on a thin roof that could not handle the weight, resulting in the collapse. Private construction workers were repairing a leak at the time. The contractor was removed from the premises and an investigation was started. The FF Plus believed the entire health infrastructure in the province was collapsing. It urged the infrastructure department to be more thorough with checks on contractors to avoid future catastrophes.'There must be accountability'The party said committees in the Gauteng legislature were often told of work not done properly, or jobs left unfinished because the contractor was either unqualified, or had ran out of money."Construction work comes to a standstill while the provincial government must go to court to get contracts suspended and to appoint new construction companies," said FF Plus MPL Philip van Staden.DA MPL Jack Bloom called for an urgent infrastructure check at the hospital. A report dated 2012 had contained warnings of structural problems in the building, he said.He wanted to know how the contractor was appointed, and recommended that future maintenance should be made the responsibility of the hospital's management."There must be accountability for this terrible tragedy that should serve as a wake-up call to give a far higher priority to maintenance and repair of our hospitals."According to the infrastructure department's website, the Gauteng government planned to spend R42bn on socio-economic infrastructure programmes in the next three years.A "maintenance crack team" had already implemented a pilot project of revitalising the Orlando Clinic dental ward.