The authorities of Johannesburg have identified the cause of the mysterious explosion in the city’s downtown, with the investigation revealing that the cause was methane gas, local media reported, citing City Manager Floyd Brink.
Fire specialists, international engineers, structural experts and professionals in occupational health and safety were involved in the investigation process, according to the media.
Brink also noted that $200,000 have already been spent on professional experts’ services, site cording, technology, and temporary relief services.
The city plans to restore the 90-year-old tunnels in compliance with international and South African standards. This includes upgrading the tunnel's structure so that it could withstand a 9.5% methane explosion, installing continuous gas detection and alarms, the official said.
On July 21, apart from the methane gas, the city authorities named a malfunction in the sewage rainwater system as a possible cause of the explosion. However, this option as well as terrorist action, foul play, negligence, or intentional release of gas into the tunnel was ruled out by the investigation.