MEXICO CITY: Mexican President Andres Manuel Lopez Obrador on Wednesday rejected any link between his austerity drive and a metro line disaster that left 25 dead, as devastated families began to bury the victims.

The tragedy that struck on Monday night, when a section of elevated track collapsed in the capital and brought a train full of passengers crashing down, has left the country in shock and mourning.

"I have no words to describe the pain," said 31-year-old Luis Adrian Hernandez.

"My father's dead and nobody can bring him back," he said, as the first funerals were held for the people who lost their lives, including a 12 year-old boy.

Foreign governments offered condolences, including US President Joe Biden, who said his country was "ready to assist Mexico as it rebuilds from this tragedy."

As allegations of administrative mismanagement of the line mounted, Lopez Obrador rejected suggestions from employers' association Coparmex that the accident was linked to public spending cuts.

"The metro maintenance has a sufficient budget. It's authorized by Mexico City's legislative assembly. What does that have to do with austerity?" the left-wing populist said.

He accused Coparmex of being part of the conservative opposition.

Yet an investigation being carried out by prosecutors and Norwegian engineering company DNV could bring more awkward questions for a president who has promised to fight deep-rooted corruption.

The authorities have also come under fire from one of the metro labor unions, which said that its earlier warning about damage to the overpass that collapsed was ignored.

"The workers are afraid, we have no guarantees," union leader Jesus Urban told the Milenio newspaper.