Jakarta. The Jakarta Police will summon two witnesses for questioning in the pornography investigation against Rizieq Shihab, leader of the hardline Islamic Defenders Front, or FPI.

Firza Husein, the woman who allegedly sent naked pictures of herself to the firebrand cleric on mobile messaging application WhatsApp, and her friend Emma, will be asked to attend further questioning.

"Firza and Emma will be summoned tomorrow to acquire additional information. After an evaluation, [we found that] there were still some missing [details]," Jakarta Police spokesman Sr. Comr. Raden Prabowo Argo Yuwono said on Monday (15/05).

He added that the questioning sessions are scheduled for 10 a.m. on Tuesday, and that investigators will only take the two witnesses' statements.

Argo said investigators also questioned expert witnesses on Monday.

"We have [expert witnesses] from Inafis [the Indonesian Automatic Fingerprint Identification System unit]," he said.

Screenshots of the WhatsApp conversations, allegedly between Rizieq and Firza, previously went viral on social media.

In addition, a recorded phone conversation, allegedly between Firza and Emma, also went viral.

Many of Rizieq's supporters consider the pornography case against their leader as a conspiracy to silence him.

The police refuted the allegation by saying, "we only follow the legal process in a professional manner after someone files a report."

Police last week said they plan to take Rizieq by force once he returns to Indonesia, after he failed to comply with two earlier summonses.