Tlahuelilpan, Mexico - Claudia Zacarias Hernandez heard the screams as flames engulfed dozens who had gathered to collect fuel from a gushing pipeline in rural Mexico last week.

She was on the other side of the field in the small town of Tlahuelilpan, about 105km north of Mexico City, when the pipe exploded.

"All those who had been burned were yelling," she told Al Jazeera, as she sat on a small bank on the edge of the field, awaiting any news on her nephew who had gone missing.

"There were children here," she said, the towers from the giant Tula fuel refinery visible in the distance. "I feel terrible because I could not help. All the burned were screaming and I could not help them."

Hernandez's nephew, Martin Alfredo, is one of the dozens who remain missing after the explosion on Friday that claimed 89 lives and injured 51, officials said on Monday.

Hernandez joined dozens of others who combed the field this weekend, looking for any sign of hope that their loved ones were still alive.

Among them was Christopher Neri Carillo, who clutched a piece of paper with a man's face as he wandered around the field on Saturday. The man is his missing father.

"Up until this moment, we don't know exactly what happened to him," Carillo told Al Jazeera.

"We know that he left the house but he hasn't come back yet," he said on Saturday. "I'm worried because I can't find him and I don't know if he's alive, if he's in a hospital and if he's seriously hurt or if he's okay and is recovering. It's horrible."

As of Monday morning, Carillo still had no word on his 48-year-old father.

Crackdown on fuel theft

The explosion came amid a fuel crisis in Mexico, which residents in the area blamed on the government's crackdown on fuel theft.

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Andres Manuel Lopez Obrador, who took power late last year, has targeted the thieves, known as huachicoleros, by cutting off the supply through the pipelines most favoured by saboteurs.

Trucks and rail cars have been employed to move fuel around the country, often with police escorts, while the pipelines sit idle. But the strategy has proven less efficient in transporting fuel, leaving Hidalgo, where Tlahuelilpan is located, among more than half-a-dozen states facing shortages at the pumps.

According to Gonzalo Monroy, the head of Mexico-based energy consulting firm GMEC, the state-owned oil firm, Pemex, was in a rush to open the pipeline due to the shortages, Reuters news agency reported. He disputed reports the pipeline had been illegally tapped.

An engineer from Pemex told reporters on Monday that the leak was initially a "small puddle", but later grew into a "fountain". Mexican Attorney General Alejandro Gertz said the incident will be investigated to determine if any negligence occurred. Pemex maintains it followed protocol.

It could be months before some of the bodies recovered from the scene are properly identified, Hidalgo Governor Omar Fayad Meneses said.

Farmworker Gerardo Perez was about 500 metres away from the field at the time of the explosion.

"The explosion was very strong because there was so much gas around. It happened in just a second. No one knew that was going to happen," he said.

The government said on Saturday that it would set up programmes in the states of Hidalgo, Mexico State and Pueblo, aimed at educating people about the dangers.

But Perez said it's not that people wanted to take the oil, but they needed to.

"We work like crazy, but at the moment there's nothing," he said, referring to a two-week shortage. "In some way, we need to get it."