It's reported by Reuters.
The El Universal newspaper clarifies that the tragedy happened on the eve of Monday, at 22:25 local time (6:25 Tuesday Moscow time). Specialists went to the scene to help the victims.
According to the newspaper El Pais, referring to the local authorities, the incident occurred while the train was passing between the stations "Olivos" and "Tesonco". In her Twitter, the mayor of Mexico City, Claudia Scheinbaum, wrote that she also drove to the crash site. Later, she clarified that she was already in place and coordinated the work of the situation center. She confirmed the death of 20 people.
At the moment, 34 injured have been hospitalized.
Note that the Mexico City metro is one of the largest metros in North America.