At least seven people, including four children, were killed when a gas explosion ripped through a government hospital here Thursday, a media report said.

More than 50 people were injured, among them 22 children, CNN quoted Mexico City Mayor Miguel Angel Mancera as saying. Besides, an unknown number of people were trapped inside the building, according to the mayor.

A truck was supplying natural gas to the Cuajimalpa Maternal Hospital on the southwest outskirts of Mexico City when apparently a hose burst and the resulting leak caused an explosion, Mancera said.

The Red Cross said it provided 23 ambulances and more than 40 people were engaged in rescue efforts.

The gas truck belonged to Gas Express Nieto, a natural gas provider among the four biggest gas distributors in Mexico, according to the company.