Mexico City, May 8 (EFE).- The death toll from the explosion of a fuel truck on a highway in Ecatepec, a city in central Mexico, has risen to 22, with more than 30 other people injured, officials said.
Two critically injured people were flown to a hospital in Houston for special treatment.
About half of those killed in Tuesday's accident were children, officials said.
The cause of the accident has not been determined, officials said.
The explosion occurred around 5:00 a.m. Tuesday between the communities of San Jose Xalostoc and Santa Clara at kilometer 14 of the Mexico City-Pachuca highway, officials said.
The accident happened when Omar Diaz Olivares, identified as the driver of the Termogas truck, lost control and hit several other vehicles, igniting his load of fuel and setting off a huge blast and fire.
Diaz Olivares survived the accident but is listed in serious condition at a hospital, where he is under guard.
The Mexico City-Pachuca highway was shut down for several hours on Tuesday at kilometer 14 in an area of the Valley of Mexico plagued by heavy traffic.
One of the fuel truck's tanks came off and the other exploded in the collision, producing a "pretty powerful explosion" that was felt "over several blocks," Ecatepec Mayor Pablo Bedolla told Milenio Television.
Ecatepec is in Mexico state, which surrounds the Federal District and forms part of the Mexico City metropolitan area.
The federal government is investigating the accident, President Enrique Peña Nieto, a former governor of Mexico state, said.
"I have instructed the Transportation Secretariat and the Government (Secretariat) to assist and take part in the efforts via the emergency management office," Peña Nieto said.
Pope Francis on Wednesday said in a telegram sent by the Vatican he was saddened by the deaths in the accident in central Mexico.
Mexico state Gov. Eruviel Avila is visiting Italy and plans to meet with the pontiff.
Avila was originally scheduled to return to Mexico on Friday but is heading home a day early.