Mexico City rescue teams are searching for survivors after a deadly basement explosion in one of the city's tallest buildings.

The Thursday afternoon blast killed at least 25 people and injured more than 100.

The building stands next to the iconic, 51-story Permex Tower. The basement and the first two floors collapsed.

"It was an explosion, a shock, the lights went out and suddenly there was a lot of debris," employee Cristian Obele told Milenio television. "Co-workers helped us get out of the building."

"I profoundly lament the death of our fellow workers at Pemex. My condolences to their families," Mexico's President Enrique Peña Nieto said via Twitter.

There is still no official word on what caused the explosion.