A powerful explosion at the headquarters of state-owned oil monopoly Petroleos Mexicanos left at least 25 dead and 101 injured, according to the Mexican government's latest bulletin.
Authorities have not indicated the cause of Thursday's blast, but local media said it could have been triggered by an overheating problem in the electrical system.
A stream of ambulances and police and military vehicles rushed to the Pemex complex, made up of a 51-story tower and several adjacent buildings and located in the capital's west-side Anzures neighborhood, in the hours after the explosion occurred.
Mexico's interior minister, Miguel Angel Osorio, said in a press conference at the Pemex headquarters Thursday night that 17 women and eight men were killed in the blast.
He said "national and international experts" would take part in the investigation into the explosion, which occurred at around 3:40 p.m. in the basement parking garage of the B2 building that houses the offices of Pemex's refining subsidiary.
The blast caused "major damage" to the basement garage and the two floors directly above it, Osorio said.
Numerous shattered windows and structural damage could be observed from outside the complex, the workplace for some 10,000 people.
"I was on the bottom floor when I felt the explosion. When I saw what was happening I tried to run, but I was thrown by the explosion, I was injured and broke a finger," Jesus Eduardo, a 23-year-old maintenance worker, told Efe.
"First I saw a co-worker who had his legs severed and next to him a lot of people dead," he added.
In his press conference, Osorio said President Enrique Peña Nieto had given instructions "to remove the last piece of rubble" to make sure that no more people are trapped.
Although there were initial reports of as many as 30 people trapped inside the complex, the government later issued a correction and said no precise figures are available.
Peña Nieto and other top federal government officials traveled to the explosion site, which was cordoned off by army and police. EFE