A natural gas explosion wrecked a tall apartment building in the Argentine city of Rosario, killing at least eight people, injuring 63 and causing an evacuation of much of the downtown.

Dozens of people were trapped in the upper floors of the burning building on Tuesday as a huge plume of smoke went up over the country's third-largest city. The building's front and back facades were ripped open, exposing the shattered remains of apartments inside.

Rosario, Argentina

Firefighters working from above and below pulled people out of windows and off balconies as the bottom floors burned. The explosion damaged other buildings for blocks around, and fearing a collapse, police closed buildings and schools in a five-block radius.

Rescuers were still looking for people in the rubble.

Rosario Civil Defence Chief Raul Rainone said the explosion appeared to have been caused by a gas leak and confirmed that at least eight people were killed in the blast.

The Litoral Gas company cut off gas flow to much of downtown.

Municipal health secretary Leonardo Caruana told Todo Noticias that the injured were being treated in hospitals across the city and that three of them had critical injuries.

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Police help an injured woman after a gas explosion at an apartment building in Rosario, Argentina. (Juan Giovacchini/Reuters)

The fire took three hours to extinguish and left the building in serious danger of collapse, firefighters said.

Buildings were damaged for several blocks surrounding the blast, which sent bricks, glass and concrete crashing onto the street.

Eleven schools were evacuated, and several shops and other apartment buildings were damaged.

Security Secretary Sergio Berni offered the services of the border police and coast guard to help local authorities.