Mexico's Foro TV
reported details of the blast and that the Red Cross are urgently seeking blood donors to help the injured.
The blast is thought to be the result of a gas buildup in the building's basement.
President Enrique Peña Nieto directed the rescue effort from inside the building in Mexico City and said, "The priority at this time is to attend to the injured and to safeguard the physical integrity of those who work [at the site]."
Shortly after the blast, the building was evacuated with the help of police, city rescue crews and Mexican Army personnel. Initially there were reports that people were trapped in the building after the explosion, but the claim was soon dismissed by the country's interior ministry.
The Government has reportedly taken tentative control of the building's administration in the aftermath of the explosion. The President's office tweeted that many of those injured were taken to Pemex Central Hospital.
Shortly after the explosion, President Nieto vowed to discover the cause of the disaster.
"We will work exhaustively to investigate exactly what took place, and if there are people responsible, to apply the force of the law on them," he told the media before visiting survivors in hospital.
María Concepción Andrade
, 42, a resident on the same block as the Pemex building, told the media, "We were talking and all of sudden we heard an explosion with white smoke and glass falling from the windows."
"People started running from the building covered in dust. A lot of pieces were flying," she added.
Gabriela Espinoza, 50, a Pemex secretary for 29 years, was reportedly working on the second floor of the building when she heard two loud explosions and a third smaller one.
"There was a very loud roar. It was very ugly," she said.
is reporting that Pemex had confirmed the explosion and had claimed that they have had electricity problems.
Images and local news broadcasts from the scene showed people being carried out on stretchers, with smoke billowing from the base of the building.
According to a government official, speaking on condition of anonymity, preliminary investigations are pointing to a gas boiler explosion. However, he stressed that nothing had been confirmed as certain.
Originally it was reported that 25 were dead and 100 people were injured. Regrettably, RT News
has just reported that the number of dead has risen to 32, with 121 people injured. No further news is yet available as to the cause of the explosion.