Officials say an elevated section of Mexico City’s metro collapsed and at least 23 people have been killed. Mayor Claudia Sheinbaum said people could still be trapped inside the train, which plunged toward a busy boulevard late Monday. It was one of the deadliest accidents for the city’s subway system, which is among the busiest in the world. One subway car left was dangling, and rescuers searched it for a time. Those efforts were suspended early Tuesday because of concerns for the workers’ safety. A crane was brought in to help shore up the car. Officials say about 70 people were injured.