Some white substances were left at locations along Armenian Street and Waterloo Street between Jan. 17 and Jan. 18, according to reports made to the police.
The substances were found one day apart at the Catholic Centre at Waterloo Street and Bible House at Armenian Street.
Subsequently, two men and nine women, aged between 49 and 67, were identified and are assisting in police investigations.
The substances were also confirmed to be harmless after a sample was collected by the Singapore Civil Defence Force (SCDF).
Three people arrested
Of this group, two men, aged 52 and 66, and a 63-year-old woman have been arrested, the police updated on Jan. 23.
The police also said that the white substances were believed to be ash from burnt newspapers, table salt and vegetable oil.
They have been seized from the 52-year-old man.
Police investigations into an offence of Public Nuisance under Section 268 of the Penal Code 1871 are ongoing.