What caused the explosion in jhb? Officials from Gauteng province, which includes Johannesburg, suspect the blast may have been caused when some underground gas pipes ruptured. Addressing the media on Thursday, Premier Panyaza Lesufi said 12 people are still being treated in hospital for their injuries. A preliminary inquiry did not establish the cause of the blast and investigations are underway to determine what happened, he told reporters. Local supplier Egoli Gas said on Thursday that they had found a small leak in one of their pipes, but they believe it is unlikely that it led to the explosion. The firm has been asked by authorities to check on their other pipes in the area, as a possible gas leak is still the focus of investigations. On Wednesday evening, witnesses reported feeling the ground shake and then hearing a loud bang moments before the earth opened, and a section of Bree Street collapsed.