JAKARTA - An explosion at a mosque inside a school in Jakarta, the capital of Indonesia, during Friday prayers injured 54 people, the city's police chief Asep Edi Suheri said.

The blast occurred around noon on Friday in the mosque, which is located within a Navy compound in North Jakarta. Police said the cause of the incident is still under investigation.

Witnesses said the explosion came from the rear section of the mosque's main hall. Police and navy personnel immediately cordoned off the area, and a bomb squad has conducted a full inspection of the site.

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Initial investigations suggested that an electrical short circuit or a malfunctioning electronic device might have caused the explosion.