The bodies of some of the 32 people killed in an explosion at a fireworks market outside Mexico City are so badly charred that neither their age nor gender can immediately be determined, the state prosecutor has said.
Alejandro Gomez said forensic experts were carrying out DNA tests to identify the blackened remains of the dead.
So far, only 18 bodies have been identified.
More than 70 people were also injured when the explosion happened.
The death toll increased from 31 to 32 later on Wednesday when one of the injured died in hospital, said Mexico state Health Secretary Cesar Gomez Monge.
Among them were three badly burned children who are being taken to a hospital in the US for treatment.
Mexico state Governor Eruviel Avila said other victims would be transferred to a specialised burn centre in Galveston, Texas, if doctors say they are fit to travel.Image copyrightAFPImage captionImage copyrightAFPImage caption
The blast and accompanying series of smaller explosions caused devastation at the San Pablito fireworks market in Tultepec, located close to Mexico City. It is estimated that about 80% of some 300 stalls in the market were destroyed.
An investigation into the causes has been ordered by the attorney general's office. It said the incident began with six initial explosions, followed by a series of chain reactions.
But Mr Gomez said he had no idea at present what triggered the disaster.
"I have no theories for now," he said. "Our priority has been to attend to the injured, remove the bodies and deal with the emergency."
Locals on Wednesday have been told to avoid the area and keep roads clear.Image copyrightAPImage caption
Survivors have spoken of "hellish scenes" as fireworks took off in all directions, causing panic and destruction. The main part of the fire is reported to have lasted at least three hours.
The disaster took place as the market was crowded with revellers buying fireworks in advance of Christmas and New Year celebrations.
Tultepec is seen by many Mexicans as "the country's capital of pyrotechnics", the Washington Post reported, with thousands of people attending the biggest festival in March - which consists of a firework display and bulls rampaging through the streets.
The San Pablito market was heavily damaged by similar fires in September 2005, when a chain of explosions just before the country's independence day celebrations injured dozens of people.Image copyrightAFPImage captionImage copyrightAFPImage caption