A gas tanker truck explosion rocked Mexico City on Wednesday, killing three people and injuring at least 70 others, including young children.

Authorities said the tanker, which was carrying more than 13,000 gallons of fuel, tipped over beneath a busy highway overpass before igniting. The resulting massive fireball engulfed nearly 30 vehicles, leaving some victims with severe burns as emergency crews rushed to control the blaze.

The injured included a baby and a 2-year-old child, both treated for burns among dozens of others who suffered serious injuries. Witnesses described scenes of chaos, with people fleeing vehicles consumed by flames and others lying in the road waiting for medical aid.

Mexico City Mayor Clara Brugada declared the incident an “emergency”, while prosecutors launched an investigation to determine what caused the tanker to flip and spark the deadly explosion.

The tragedy underscores longstanding concerns about the transport of hazardous materials through densely populated areas of the capital.