MEXICO CITY: Demands for justice mounted Thursday as relatives buried the victims of Mexico City's metro disaster, accusing the authorities of negligence that cost the lives of 25 people.

President Andres Manuel Lopez Obrador has rejected accusations that his austerity drive was a factor in Monday's accident, when a section of elevated track collapsed, bringing a train crashing down.

But at funerals in the capital, devastated families demanded an explanation for how the tragedy occurred and called for those at fault to be held to account.

"It wasn't our fault. The authorities are responsible," 17-year-old Luis Diaz told AFP after burying his father Juan Luis Diaz, who usually traveled by bus, but on the day of the accident took the metro instead.

"We were not the only ones affected. Other people also lost their relatives. Many people are injured," he said.

Luis Hernandez, whose father was also among the dead, said that he wanted "justice for my mother, because my father was the breadwinner of the household."

The 61-year-old was traveling in one of the two carriages that fell when the overpass collapsed.

"My father's dead and nobody can bring him back," Hernandez said.

"We're going to file a lawsuit, but right now we want to get through all this," his mother said, crying inconsolably.

The victims also included a 12-year-old boy, Brandon Giovanny, who was laid to rest on Wednesday.

Mexico City Mayor Claudia Sheinbaum told a news conference that Norwegian engineering company DNV, which has been tasked with helping prosecutors with the investigation, would carry out "a root cause analysis" of the accident.

"That is, what's caused this situation in general terms since its construction," she said.