At least one person allegedly involved in a recent protest on an MRT train has been questioned by the police.
Mr Sean Francis Han, who is an activist and the editor of wakeupsg.com, was seen entering the Police Cantonment Complex at New Bridge Road around 9.30am. He was seen leaving about two hours later.
When asked, the police reiterated that they were looking into the matter.
The protest, staged to highlight detentions that had happened 30 years ago under the Internal Security Act, was held on a North-South Line train on June 3.
Photos posted online showed at least seven blindfolded people holding up books with the title 1987: Singapore's Marxist Conspiracy 30 Years On. The book was launched last month by ex-detainees to mark the anniversary of their arrests.
In May 1987, 22 people were arrested in Operation Spectrum and were accused of being involved in a Marxist conspiracy to establish a communist state.