Supermarket chain FairPrice has filed a police report over online rumours that its house brand jasmine fragrant rice is made of plastic.

Addressing a post on social media that contained the fake claim, FairPrice said its rice has passed safety checks by the authorities.

"We would like to advise the public not to further circulate this false information which may cause unnecessary public alarm," said its corporate communications director Jonas Kor.

The chain will put up notices at stores about the rumour which has been circulating via text and on social media since Tuesday.

Several alarmed customers had gone to FairPrice stores to demand refunds yesterday.

FairPrice has been selling its house brand jasmine rice, sourced from Vietnam, since 2008.

Those who suspect that the rice they bought is fake may approach the Agri-Food & Veterinary Authority (AVA) to verify its authenticity.

The authority regularly inspects and samples imported rice to ensure it complies with Singapore's food safety standards and requirements. The sampling includes testing for mycotoxins, pesticide residues and heavy metals.

The AVA in December said it had not detected fake rice in Singapore.

This is not the first time FairPrice has been a target of false news.

In 2015, a fake social media post asked users to share a link on their Facebook page in order to claim a $100 FairPrice coupon.

In 2007, FairPrice lodged a police report after it found a picture of "halal pork", allegedly sold by its stores, circulating on the Internet.

The image, which resurfaced online in 2014, is fake.