The financial trader charged with orchestrating what police describe as one of Singapore's biggest suspected investment frauds began setting off alarm bells at banks more than a year before his arrest in February, according to a Bloomberg report citing people familiar with the matter.

Ng Yu Zhi's unusually large cash transfers from his trading company to his personal account prompted Oversea-Chinese Banking Corp to file suspicious transaction reports to police as far back as 2019, the people said, asking not to be identified discussing private information.

The bank shut his personal account in August 2020. Ng's corporate account at United Overseas Bank was closed more than a year before the 34-year-old was arrested, one of the people said.

The previously unreported timeline raises fresh questions about how Ng could have maintained an alleged $1.46bn fraud for so long, new agency Bloomberg said.