NEW: Three men have been taken into custody in connection with the blast
NEW: A baby injured in the blast has died, bringing the total number of fatalities to 3
Mexico City's mayor says a gas leak was reported, then there was an explosion
Two of men in custody are hospitalized, and a third, with less serious injuries, was checked at a hospital.
More than 100 people were inside Cuajimalpa Maternal Hospital when the blast occurred at about 7 a.m., minutes after a hose burst on a truck supplying gas to the building. Paramedics carried bloodied victims on stretchers.
Ivonne Lugo Durantes told CNNMexico she spent 10 minutes trapped under rubble before rescuers reached her.
The supervising nurse called her husband, Mario Angeles Sanchez, after the blast. As she described what was happening, he heard people in the background screaming for help.
“I am still a little bit in shock. It was a nightmare,” she said, describing how hospital workers tried to rescue babies from a nursery as flames engulfed the building.