The anti-government activist who lied about being assaulted to cover up cosmetic surgery was detained by Jakarta police last Friday night and will be held for the next 20 days.
Ms Ratna Sarumpaet is at the centre of a bizarre saga that has swept up prominent members of the opposition camp, including presidential hopeful Prabowo Subianto.
She was a member of the campaign team for Mr Prabowo, President Joko Widodo's rival in the April 2019 election, until she resigned last Wednesday over her lie.
A police spokesman said Ms Ratna, 69, is being held "so she will not run away or get rid of evidence".
She is suspected of spreading fake news that could cause unrest and spreading lies and hate speech. Both violate Indonesian law.
Ms Ratna, who could be jailed for 10 years if convicted, was stopped at the airport on Thursday night as she tried to leave the country.
She said she was not fleeing to avoid prosecution but was headed to Chile to attend a conference.
Ms Ratna grabbed headlines when photos of her bruised face went viral last Tuesday. She said she had been attacked by three men in Bandung, West Java, on Sept 24.
But just a day later, after police said they had evidence that she had been in an aesthetic hospital in Jakarta at the time of her supposed attack, she confessed she had lied.
The bruises on her face, she said in a tearful press conference, were the side effects of a cosmetic procedure, and she had been in a Jakarta hospital from Sept 21 to Sept 24.
Investigators said they also found that Ms Ratna paid for the treatment from a bank account used to collect funds for victims of the June 18 Lake Toba ferry tragedy in which over 150 people were missing and presumed dead.
But they said there was no confirmation that she had dipped into the donations to fund her procedure.
Ms Ratna last Friday denied misusing donated funds, telling reporters repeatedly: "No."
Members of the opposition camp taken in by her lies have denounced her actions, with Mr Prabowo - who rallied behind her on Tuesday - apologising two days later "for amplifying something we were convinced was true".
Mr Prabowo's running mate, Mr Sandiaga Uno, said last Friday that they would both be prepared to provide statements to the police about the hoax if needed.
Jakarta Governor Anies Baswedan defended the provincial government's sponsorship of Ms Ratna's trip to Chile.
The Jakarta Culture and Tourism Agency said on Friday that she had been slated to attend the 11th Women Playwrights International Conference, for which she is a senior adviser, adding that Ms Ratna - a former actress - had asked for sponsorship in January.
Mr Anies said the request was processed in February and "everything has been done since a long time ago".
"We provided this support because she was once chairman of the (Jakarta) Arts Council. So this is a normal process which happens with many artists in Jakarta," he said last Friday.
Ms Ratna - a staunch critic of President Joko - has had a long history of courting controversy, taking to social media with sensational claims that were later proven wrong.
Last year, she posted on Twitter that the government had sold state aircraft manufacturer Dirgantara Indonesia to China. She apologised when the firm denied her accusation.
Earlier this year, she claimed that the government had issued a 200,000 rupiah note because of the weakening rupiah.
Bank Indonesia, responding to Twitter users sharing her post, said it was a hoax.