Rescuers are searching for survivors and authorities have promised a thorough investigation after an office building blast killed 32 people and injured 121 at the headquarters of Mexico's state-owned oil company.
The cause of the basement explosion in an administrative building next to the 51-storey Pemex tower in Mexico City remains a mystery, with President Enrique Pena Nieto urging people not to speculate. Theories ranged from an electrical fire to an air conditioning problem to a possible attack.
"We have no conclusive report on the reason," Mr Pena Nieto said. "We will work to get to the bottom of the investigation to find out, first, what happened... and if there are people responsible in this case, that we apply the full weight of the law against them."
Petroleos Mexicanos director Emilio Lozoya said the death toll had risen to 32, with 121 people treated for injuries after Thursday's blast. He said 52 remained in hospital and rescue efforts continue, as survivors and bodies may still be found in the rubble.
More than 500 firefighters, soldiers and rescue workers dug through chunks of concrete, aided by dogs, trucks and a Pemex crane.
The explosion happened in the afternoon, just as the administrative shift was about to end. It hit the basement and three floors, where as many as 250 people work, Mr Lozoya said.
The floors collapsed in the 14-storey administrative building at the headquarters office complex, where some 10,000 people work daily. Mr Lozoya said about 1,700 work in the building affected.
"There is a lot of risk," rescuer German Vazquez Garcia said of working on the site.
Gabriela Espinoza, 50, who has been a Pemex secretary for 29 years, was on the second floor of the tower when she said she heard two loud explosions and a third smaller one. "There was a very loud roar. It was very ugly," she said.
The injured were taken to two Pemex hospitals and other facilities, including a Red Cross hospital. Relatives huddled in the waiting room for news of their loved ones. Some walked out of meetings with the hospital social worker joyous, while others came out crying.