The city of Mexico explosion kills 25

February 1, 2013 Last updated at 06:39 GMT that will Grant to the BBC said the explosion happened "at the worst possible time"

The number of people killed by an explosion in Mexico City at the headquarters of the national oil company, Pemex, has risen to 25, the Minister of the Interior said.

At least 100 people were injured and an unknown number trapped in the rubble at the base of the 54-story tower. The search for survivors continues.

The cause of the explosion is under investigation, said Pemex.

Last September, 30 people died in an explosion at a Pemex gas refinery in the North of the Mexico.

Anxious parents

Thursday's explosion in the lower floors of the building which happened as shifts were changing in the afternoon, making this particularly cluttered area.

Television footage showed debris from the explosion spread in the street before the building and ambulances of the Red Cross on the scene, attending to the wounded.

The building of Pemex's 54 floors is 214 m (702 ft) in height

Hundreds of rescuers, aided by dogs looking 30 people supposed to be trapped inside the building.

Police have cordoned off the streets around the building, which is located in a shopping area of the city of Mexico.

PEMEX said its operations will continue to operate normally - and commercial and financial obligations will continue to respect - despite the explosion.

Director general sound, Emilio Lozoya Austin, cut short a business trip to Asia and went to the Mexico, a Pemex statement said.

Members of the family of employees are gathered before the building looking for information about their relatives, local media report. It said that some have tried to reach employees on their mobile phones, but have had no response.

"The place shook, we lost power and all of a sudden there's debris everywhere. Colleagues helped us out of the building, "an eyewitness said Cristian dagger.

"We were talking and all of a sudden we heard an explosion with white smoke and glass falling from the Windows," another witness said.

"People began to flee the dust covered building. Many pieces were flying. »

Continue reading the main story Will Grant BBC News, Mexico City

Pemex's construction in the North of Mexico City is surrounded by a large number of police and paramedics. Sniffer dogs are used to search for people trapped under the rubble.

Mexico City is used to earthquakes, and emergency services seem well prepared for this type of disaster.

The skyscraper has withstood the explosion also, with most of the damage limited to the ground floor and first floor. But night has now in the Mexican capital, which complicates the search.

Some members of the families of the missing workers gathered outside the Pemex, construction of the news of their loved ones, while others are are made directly to hospitals.

Authorities and teams of paramedics release information at regular intervals, but the exact cause of the explosion can still take a long time to be confirmed. This is now by far the worst explosion in Mexico for nearly 30 years.

Images of the explosion posted on Twitter showed large clouds of smoke rise up of the building. Television images showed people transported by helicopter from the scene.

The President Enrique Peña Nieto and Mayor of Mexico City Miguel Angel Mancera led on the site of the explosion.

Mr. Peña said Pemex rescue and security teams working alongside the authorities in the city to help the wounded.

"I am deeply sorry for the death of our colleagues at Pemex. My condolences to their families, "Mr. Peña said on Twitter.

"For the moment, the priority is to help the wounded and protect the physical security of the people who work there."

The President said that he has ordered an investigation into the causes of the explosion.

Earlier on Thursday, Pemex had reported problems with the electricity in the building, in a message on Twitter.

Later, he confirmed that an explosion had taken place "in building B2 from the administrative centre".

Plaster fell from the ceiling of the basement and the situation was "delicate", a local emergency services spokesman, quoted by the news agency Reuters said.

PEMEX has experienced a number of fatal accidents in recent years.

Deadly explosion of last September in a refinery of gas near the northern city of Reynosa appears to have been caused by a buildup of gas.

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