A large cavity discovered beneath a highway bridge on Johannesburg’s M2 has prompted warnings about the wider effects of illegal mining on critical infrastructure. The Johannesburg Roads Agency (JRA) says the excavation under the bridge is evidence of extensive underground damage in the area, and that repairs could be costly. The incident draws attention to the risks that illegal mining poses not only to local ground stability, but also to transport assets that depend on stable foundations. While the reports focus on the bridge site, the JRA warning suggests similar damage may exist beyond the immediate location, implying that the underlying problem is broader than a single defect. The JRA’s response includes raising concern over potential impacts on the safety and integrity of the roadway and structures connected to it, and underscores the need for assessment and remediation. Overall, the cavity under the bridge is presented as a visible sign of illegal mining activity and its possible consequences for infrastructure in Johannesburg.