Jakarta Police arrested four people on Wednesday for running a meat processing factory that allegedly mixed pork into what is supposed to be pure beef meatballs, which are used in the popular soup better known here as bakso.

The arrest was made during a joint raid of the factory near Cipete market in South Jakarta by police and the farming and fisheries unit of the South Jakarta administration. The factory has supplied meatballs to bakso vendors in Jakarta.

"[The operators] had been mixing beef and pork to produce meatballs in this meat processing factory," an official with the Jakarta administration, Nurhasan, said in Jakarta on Wednesday.

"Prior to this [raid], we gathered samples of the processed meat, and they tested positive for pork," he added, according to the official news website of the Jakarta administration, beritajakarta.com.

In majority-Muslim Indonesia, consumption of pork is considered haram (forbidden under Islam) by many.

Nurhasan said police detained the owner of the factory, Eka Prayitno, and three of his employees. Police also questioned two bakso sellers that were seen at the location.

Police also seized 50 kilograms of pork and 15 kilograms of processed meat containing beef and pork from the factory.

Nurhasan said the factory had operated for two years, although it was not clear when its operators began adding pork to the meatball mixture. He added that the suspects did the mixing to bolster profit margins, citing relatively higher beef prices.

The suspects are charged with violating a Jakarta meat trade and slaughter monitoring bylaw, and face up to three months in jail and Rp 5 million ($520) in fines.