Police said they were investigating top daily The Straits Times over a voter survey it conducted ahead of a by-election in apparent breach of a law against polls during the campaign.
The by-election on January 26 is for a seat left vacant when the former speaker of parliament, Michael Palmer, stepped down after confessing to an extramarital affair.
The Elections Department said an article published by the English-language newspaper on January 10, a day after the election was called, was "currently being looked into by the police."
Police confirmed the investigation. The Straits Times itself disclosed the investigation on its website late Sunday and said it would co-operate with police.
The issue carried a report on a poll it conducted among 50 residents in the contested ward. The article was headlined "ST poll: More rooting for PAP".
The PAP, or People's Action Party, has been in power since 1959. "This was not a full-scale survey, or scientific poll, by any means," editor-in-chief Warren Fernandez said. "The headline for our story overstated the significance of the information gathered by calling it a poll. We are sorry for this lapse."
The Straits Times is the flagship publication of Asian media giant Singapore Press Holdings.
In Singapore it is illegal to publish the results of voter surveys from the day the election is called until the end of polling.
Offenders can be fined up to S$1,500 (HK$9,500) or jailed for up to 12 months, or both.