It was previously reported that unidentified white substances were found at the Bible House and the Catholic Centre one day apart, resulting in people being evacuated.
2 men and 9 women were assisting with police investigations, of which a 52-year-old man, a 66-year-old man and a 63-year-old woman have been arrested.
The police added that the white substances found were believed to be ash from burnt newspapers, table salt and vegetable oil, which were seized from the 52-year-old.
An unidentified white substance was found at the Bible House in Armenian Street and the Catholic Centre, according to The Straits Times.
The substance was found sprayed on the Catholic Centre at Waterloo Street on 17 January, resulting in the occupants of the building being evacuated.
A white substance was also found at the Bible House in Armenian Street, and the Singapore Civil Defence Force and the police were deployed to the scenes.
Two men and nine women between the ages of 49 to 67 are assisting the police with investigations.
The Singapore Police Force said that they received a report of a “white substance found at a location along Armenian Street” at about 11.40am on 17 January.
The SCDF was activated to investigate, and they took a sample of the substances before running tests on it – there were no harmful substances detected.
The police are investigating the incident.
The SCDF was alerted to the incident at the Catholic Centre yesterday at about 9.55am, and they were seen outside the building with the police.
The substance was found on the walls of two sides of the building and its foyer, appearing in liquid form.
The occupants of the building were evacuated at about 10.30am, before being allowed back into the building at about 12.20pm after the police and the SCDF conducted checks.
A spokesperson for the Roman Catholic Archdiocese of Singapore said that they have lodged a police report.