A Singaporean man has been fined 1,500 Singapore dollars ($1,042) for spiking his Japanese colleague's drinking water with a "love potion" that contained poisonous substances in an attempt to make her fall in love with him, according to local media reports and court documents.

Wong Fook Hiong, a 43-year-old technical officer at the Ngee Ann Polytechnic, was slapped with the fine by a Singapore court on Tuesday for carrying out a negligent act that could endanger life. It was found the mixture contained substances listed as poisons under Singapore law.

Laboratory tests carried out during a police investigation showed that the mixture contained xylazine, a sedative meant for animals, and haloperidol, an antipsychotic drug.

Wong secretly poured the mixture into a bottle of mineral water on the 30-year-old Japanese lecturer's desk at the school in January last year.

The victim became suspicious as the drink tasted bitter, left her with a dry throat, unable to think clearly and sleep at night.

She caught Wong in the act by leaving her mobile phone on her desk with the video recording mode on. After seeing him pour the concoction into her water bottle, she lodged a police report the following day, leading to his arrest.

The Straits Times quoted Assistant Public Prosecutor N.K. Anitha as saying that Wong, who is married, admitted to the offense. Wong "claimed he had added the unknown substance in the hope that the victim would drink the contaminated water and fall in love with him."

Wong purchased the "love potion" containing an "unknown substance" online for $200.

An official with the polytechnic's public relations office said the Japanese lecturer was teaching Japanese language at the time. She left her job when her contract ended soon after the incident in March last year.