Ballot papers and other documents from the May 7 Bukit Batok by-election were destroyed yesterday.
Sealed boxes containing the documents were taken from the Supreme Court to the Tuas South Incineration Plant where they were burned.
Under the Parliamentary Elections Act, they must be sealed for six months and then destroyed, unless the President directs otherwise.
This is to ensure the secrecy of the vote.
The Bukit Batok by-election was called following the resignation of People's Action Party (PAP) MP David Ong in March over an alleged extramarital affair.
The PAP's Mr Murali Pillai won 61.2 per cent of the votes in a straight contest against Singapore Democratic Party chief Chee Soon Juan. In all, 24,224 votes were cast.