The tanker appeared to have got stuck under a low bridge on Saturday morning in Boksburg city, about 100m from Tambo Memorial Hospital. Patients were evacuated from the hospital's casualty after part of the roof collapsed following the blast. The truck was carrying liquid petroleum gas. "Apparently, a gas tanker drove under the subway bridge and got stuck in there, and due to friction, it caught alight," emergency services spokesperson William Ntladi was quoted as saying.