Deadly explosion rocks Mexico City

Deadly explosion rocks Mexico City skyscraper housing oil giant Pemex

A powerful explosion shook the building housing the headquarters of Mexican oil giant Pemex. NBC's Kristen Dahlgren reports.

Rescue workers searched through rubble Friday after a powerful explosion in the Mexico City skyscraper complex housing the headquarters of Pemex, the state oil monopoly, killed at least 25 people and injured more than 100 others, company and government officials said.

Interior Minister Miguel Angel Osorio Chong warned Thursday that the number of victims would likely rise.

Mexican President Enrique Peña Nieto arrived at the Pemex administration complex by helicopter Thursday night to supervise rescue operations, Pemex and the news agency La Prensa reported. Hundreds of Mexican military forces were sent to the complex to "preserve security," officials told newspaper El Universal.

Emilio Lozoya Austin, director general of Pemex, which is short for Petrõleos Mexicanos, was flying home from a business trip to Asia. He said he extended his condolences "to all the families of Pemex workers who have lost their loved ones."

The explosion took place in the basement garage of the auxiliary building, next to the company's 52-floor tower in a busy commercial and residential area, said Eduardo Sánchez, a spokesman for the Interior Ministry.

Stringer/Mexico/Reuters

An injured woman is transferred to a stretcher outside the headquarters of state oil giant Pemex in Mexico City on Thursday.

"They're conducting a tour of the building and the area adjacent to the blast site to verify if there are any still trapped so they can be rescued immediately," Sanchez said.

A government official, speaking on condition of anonymity, said preliminary findings suggested the blast was caused by aged boiler exploding in a Pemex building next to the tower, Reuters reported.

Authorities were still investigating Friday, however, and Peña Nieto urged people not to speculate and promised a thorough investigation.

The plaster ceiling of the basement collapsed, a spokesman for the local emergency agency said. He described conditions in the tower as "delicate."

Sánchez said as many as 30 people remained trapped in the debris Thursday. Search-and-rescue dogs were sent into the skyscraper, parts of which remained on fire at 10 p.m. ET, cloaking the Mexico City skyline in a thick cloud of smoke, Telemundo reported.

The main floor and the mezzanine of the auxiliary building were heavily damaged, along with windows as far as three floors up. 

A man who was on the ground floor when the explosion occurred told Forum TV that the first casualties were taken to a clinic in the adjacent office tower, where several thousand people work.

"It shook the building, and then we were evacuated," he said.

Company touted safety recordNews of the blast came toward the end of the business day — just a few hours after the company had sent two messages on Twitter celebrating how much it had "reduced our accident rate in recent years," announcing that its "safety indicators" exceeded international standards: