State-owned Trans-Caledon Tunnel Authority (TCTA) says a worker died after a mobile crane toppled during the cleaning of a reactor at the Central Basin acid mine drainage treatment plant in Germiston, Johannesburg, on Wednesday.According to a statement released by the company, the crane was being used to service the reactor."TCTA is a state-owned entity charged with financing and implementing bulk raw water infrastructure projects," according to its website.It said an investigation involving the Department of Labour and police had been launched after the incident."TCTA and the on-site operator will work closely with both organisations to ascertain the cause and circumstances surrounding the incident," Johann Claassens, the executive manager: project management and implementation, said."We would like to convey our most sincere condolences to the family of the deceased."Central Basin is one of three treatment plants managed by TCTA."This is the first time TCTA has encountered an incident of this nature at its three plants," it said.