Anger mounts as death toll from Mexico metro overpass collapse rises to 24

• Mexico City mayor promises thorough investigation
• Subway train crashed on to traffic on street below

The death toll from the collapse of an overpass on the Mexico City metro has climbed to 24, as crews worked to clear the wreckage - and anger grew over the latest in a string of catastrophes to hit one of the world's largest mass transit systems.

Officials refused to speculate on the cause the disaster which sent two carriages crashing into passing traffic on the street below on Monday night. The city's mayor, Claudia Sheinbaum, promised a thorough investigation by an outside firm and the federal prosecutor's office - though she stood by the embattled director of the metro, Florencia Serrania.