The death toll from a fiery explosion at the site of an illegally tapped fuel line in central Mexico rose Sunday to 79, officials said.

Hundreds of people had been drawn to the site in the  state of Hidalgo on Friday to gather fuel amid shortages and a government crackdown on pipeline fuel thefts.

The cause of the explosion is under investigation, Attorney General Alejandro Gertz told a news conference.

Health Minister Jorge Alcocer said six more bodies were found during a final search of the site in the town of Tlahuelilpan, in addition to 73 previously reported dead.

He said 66 people injured in the explosion were hospitalized in Hidalgo, while those in more serious condition have been moved to Mexico City for specialized care.

"There are patients in serious condition with burns of more than 80 percent (of their bodies)," he said, adding that their prognosis was "reserved."

The search for remains ended late Saturday but families of the victims called for the search to continue and for forensic experts to return to the scene.

Images captured by local media showed a torrent of fuel escaping from a pipeline after thieves tapped into it.

As many as 700 people had converged on the site with buckets and drums to collect gasoline when the explosion occurred.

Local media showed people screaming as they fled, their clothes in flames, some with severe burns.

Gertz said that the investigation did not seek to "victimize the communities."

"We are going to find those responsible for actions that generated this tragedy," he said. "Victimizing the whole population is not (the investigation's) function nor is it established in the law."