Dozens of people have been injured in an explosion during Friday prayers at a mosque inside a high school complex in Indonesia’s capital, Jakarta.

Fifty-four people were admitted to hospital, city police chief Asep Edi Suheri told a televised news conference, with the injuries ranging from minor to serious and including burns.

Authorities said three people had suffered serious injuries and 17 others came away with minor injuries. Others have been treated and discharged, local media reports.

The Jakarta Metropolitan Police is now investigating the cause of the explosion at the site in Kelapa Gading, a district in North Jakarta, with a bomb disposal team deployed to the search area.

Images from the scene show bystanders watching on as military personnel cordon off and guard the entrance to the state-run high school complex.

The explosion occurred around 12:15 local time (05:15 GMT), according to local reports.

A high-ranking Jakarta Metropolitan Police officer confirmed the presence of two objects resembling firearms at the scene.

Images from Indonesia’s government-owned news agency Antara suggest one of the objects appeared to be a submachine gun and another looked like a pistol.

The submachine gun-type object appears to be inscribed on its barrel with: “14 words. For Agartha.”

On its body, it says: “Brenton Tarrant. Welcome to Hell.”

Brenton Tarrant is the perpetrator of a 2019 mass shooting at a mosque and Islamic centre in Christchurch, New Zealand, that killed 51 and injured dozens of others.

A minister who visited the scene later on Friday sought to dispel suggestions that weapons were present at the site, telling CNN Indonesia what had been pictured “turned out to be a toy gun, not a real gun”.

Lodewijk Freidrich Paulus also called on the public not to presume the explosion was a “terrorist act” as investigators were still combing over the scene.

Another object found at the site was a dark green belt for storing gun cartridges.

A pupil at the school alleged to Antara that a homemade bomb had been brought in by a student who had often been bullied by other students.

Indonesia has the world’s largest Muslim population.