Having just read the article it looks to me as though it isn't the metformin that is causing the problem, but another drug called nitrosamine, N-nitrosodimethylamine (NDMA)
The HSA said on Wednesday that three metformin drugs were found to contain a type of nitrosamine, N-nitrosodimethylamine (NDMA), in trace amounts that are above the internationally acceptable level.
The named brands containing this contaminant are (according to the article)
The recalled drugs are: one batch of the Glucient XR 500mg tablet, supplied by Glorious Dexa Singapore; and all batches of Meijumet prolonged-release tablet in 750mg and 1,000mg versions, supplied by Pharmazen Medicals.
These 3 brands/batches have been recalled, so anyone with them should make sure they return them to the place they got the medication, or to the manufacturer. I am sure there is more info available in Singapore and on the Singapore news on how to do this.