At least 23 people were killed and about 70 more were injured when a metro overpass in Mexico City collapsed onto a road sending a subway car plunging toward a busy street Monday night, authorities said.

The accident, which happened near 10:30 p.m. local time, trapped cars under rubble and passengers in train cars hanging mid-air,  video on social media and Mexico television showed. Emergency crews worked to recover those passengers.

A crane was working to hold up one subway car left dangling on the collapsed section so that emergency workers could enter to check the car to see if anyone was still trapped.

Mayor Claudia Sheinbaum said 49 of the injured were hospitalized, and that seven were in serious condition and undergoing surgery.

“There are unfortunately children among the dead,” Sheinbaum said, without specifying how many.

According to the Associated Press, the overpass was about 16 feet above the road in the southside borough of Tláhuac, but the train ran above a concrete median strip, which apparently lessened the casualties among motorists on the roadway below.

“A support beam gave way,” Sheinbaum said, adding that the beam collapsed just as the train passed over it.

The AP also reported rescue efforts were briefly interrupted at midnight because the partially hanging train was “very weak” and a crane had to be brought in. There were still people trapped inside the train, but “we don’t know if they are alive,” said Sheinbaum.