RESCUE teams worked through the night to pull out survivors after a massive explosion at the main headquarters of Mexico’s state-owned oil company killed 25 people and injured 101.

Interior minister Miguel Angel Osorio Chong said 17 women and eight men died in last night’s blast.

Many casualties remained trapped in the rubble today, as soldiers with rescue dogs, lorries with mounted lights and a crane were brought in to help with rescue efforts.

The blast wrecked the basement and two floors of the Petroleos Mexicanos, or Pemex, building in Mexico City and sent hundreds fleeing into the street.

The Interior Ministry said it was unsure of the exact number trapped because many were outside having lunch when the explosion happened at about 3.45pm local time in a basement parking garage next to the famous 51-storey tower of Petroleos Mexicanos, or Pemex, one of the tallest buildings in Mexico City.

President Enrique Pena Nieto said authorities had not yet found what caused the blast in the 14-storey building in a busy commercial and residential area.

Pemex first said it had evacuated the building because of a problem with the electrical system. The company later tweeted that the Attorney General’s Office was investigating the explosion and any reports of a cause were speculation.

The tower, where several thousand people work, was evacuated following the blast but not damaged, according to Gabriela Espinoza, 50, a Pemex secretary for 29 years who was on the second floor when the explosion next door occurred.

“There was a very loud roar. It was very ugly,” she said. Her colleague, Tomas Rivera, 32, worked on the ground floor and was thrown to the ground, fracturing his wrist and jaw.

Hundreds of firefighters, military in camouflage and Red Cross workers hauled large chunks of concrete and looked for victims throughout the night, with at least four bodies pulled out of the rubble.

“We were talking and all of sudden we heard an explosion with white smoke and glass falling from the windows,” said Maria Concepcion Andrade, 42, who lives on the same block as the Pemex building. “People started running from the building covered in dust. A lot of pieces were flying.”

Police landed four rescue helicopters to remove the dead and injured and about a dozen tow trucks were furiously moving cars to make more landing room.