Police reports have been filed by angry investors who fear they have lost millions of dollars invested in a local fintech currency trading firm that built a high profile by painting its name on an aircraft and wooing potential clients in Davos, Switzerland.

SixCapital, or SixCap as the firm is called, promised returns as high as 18 per cent a year but stopped making payouts around June. Investors also had difficulties accessing their performance reports.

Around 1,000 investors and employees put millions of dollars into the fintech firm that described itself as using "big data and powerful analytics" to make currency trades.

The firm, which has an office on the ground floor of SGX Centre 1 in Shenton Way, appears to have hit trouble earlier this year.

It e-mailed clients on June 8, saying that OCBC Bank told it in May that its banking accounts could no longer be supported.

SixCap said it had been trying to open accounts with other banks since May 25, but "the KYC (Know-Your-Customer) processes these days are more stringent and take longer than before".

The company was then hit by a surge of withdrawal requests.

More recently, in a letter to investors dated Nov 10, SixCap said it had discontinued its two products, Tagg and B'Data, which earn yields for investors through foreign exchange trading.

Investors were told they could expect their principal back "over a 24-month period beginning in the second half of February 2018".

The same letter detailed the abrupt resignation on Oct 9 of SixCap chief scientific officer Abdalla Kablan and 13 of his key IT staff.

SixCap had acquired Malta-based data analysis start-up Hippo Data, founded by Dr Kablan, earlier this year.

"By now, almost all the employees in Malta have resigned and left abruptly," wrote SixCap boss and sole owner Patrick Teng Chee Wai.

The exodus brought operations at SixCap's tech firms to a halt, impacting the group's "various Ricebowl business models", he said.

Ricebowl is a forex trading model offered by SixCap.

Mr Teng said: "Ricebowl is a system being developed and refined with the help of Dr Kablan and he has in fact written academic papers on this system which were shared with the Monetary Authority of Singapore about one to two years ago."

The Straits Times could not find these papers, and Mr Teng declined to share them, citing confidential content.

Dr Kablan said he could not comment and is seeking legal advice.

Mr Teng's son, Mr Paul Teng, who was SixCap's chief investment officer, did not answer questions about Ricebowl.

He told The Straits Times last Monday : "I can't comment because I've resigned since Nov 1. I'd rather not talk about it. Ricebowl was always looked after by my dad."

One of SixCap's presentation materials states that FX B Share, the predecessor of B'Data, is governed by Singapore law and vetted by law firm Rajah & Tann.

Rajah & Tann senior partner David Yeow told The Straits Times by e-mail: "The reference to my firm in the attachment was made without prior notice or approval from my firm."

Investors in Tagg and B'Data are now asking how they can recover their money.

Some filed reports with the police and the Commercial Affairs Department last month as they want an investigation into its transactions.

A police spokesman told The Straits Times: "It is inappropriate to comment on investigations, if any."

The Straits Times visited SixCap's Shenton Way office before noon on Nov 24 but the lights were off and the door locked. A security guard said it had been closed since Nov 20.

SixCap's chief revenue officer, Ms Jaslyn Tan, told The Straits Times that Six Capital (FX Trading) had moved to Marina Bay Financial Centre Tower 3. She did not answer further queries.

The address she gave was for a serviced office space shared with about 20 other companies. The Straits Times visited the place last Tuesday and was told by a staff member that neither Mr Patrick Teng nor Ms Tan was present.

It marks a sharp turn of events for SixCap, which worked hard to raise its profile. The firm was a sponsor of some events hosted by The Wall Street Journal and CNBC, where Mr Patrick Teng would appear as a speaker.

In December last year, SixCap had its livery painted on an AirAsia jet to promote Tagg's launch in the Indonesian market.

And in January, Mr Teng and son Paul went to Davos, Switzerland, to ink a memorandum of understanding with an Indonesian university - Universitas Gadjah Mada - on the sidelines of the World Economic Forum.

SixCap's most recent product is Thundr TV, a $99 device or app that allows access to TV channels.

During Thundr's Singapore roadshow in July, Miss Universe Indonesia 2015 Anindya Putri and Miss Universe Croatia 2015 Mirta Kustan were featured as channel personalities.

For now, investors are split on what to do. Some believe SixCap will pay them back eventually, while others are not so sure.

A semi-retired freelance consultant who wanted to be known only as Mr Rao sank $20,000 in Tagg and $80,000 in B'Data. He joined a small gathering of investors on Nov 20 to discuss their next steps.

Mr Rao, 49, said: "A few retirees indicated that they had poured in significant retirement sums. One lady was the age of my mother. She said that she was going to the temple to pray."