(Updates casualties, adds info on cause of blast)

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Eight people died and 63 others were injured in a gas explosion inside a 10-story apartment building in the central Argentine city of Rosario, authorities said.

Rosario municipal prosecutor Gabriela Argüelles, confirmed the death toll, which could rise given that there are still people missing who could be buried in the ruins.

The health minister for Santa Fe province, Miguel Angel Cappiello, said that the injured are being treated at four different hospitals around the city.

The explosion occurred about 9:40 a.m. and could be heard more than 40 blocks away, witnesses said. The shockwave from the blast caused damage to neighboring buildings.

The cause of the explosion was "an incredible (gas) leak," Rosario Mayor Monica Fein told the media.

During his visit to the blast site, Santa Fe Gov. Antonio Bonfatti said that there "is ... massive destruction" in the center of the city.

The tremendous detonation forced authorities to evacuate 11 nearby schools as a precaution against a new explosion, a possibility that was later ruled out by experts at the ENARGAS regulatory agency.

Prosecutors ordered a review of the computer system of Litoral Gas, the utility serving Rosario, to determine if any local residents had called to report a gas leak before the explosion.

Company spokesman Jose Maria Gonzalez said that there was a possibility that "the gas had concentrated in a closed space and, therefore, it was not noticed by the residents of the damaged buildings."

"If a piece of equipment loses gas inside a closed space it's very difficult to notice it from outside until the concentration is very dangerous," Gonzalez told state news agency Telam. EFE