SINGAPORE - The Monetary Authority of Singapore (MAS) and the Commercial Affairs Department (CAD) are investigating broking firms for possible breaches of the Securities and Futures Act, MAS said on Friday (April 22)

Separately on Friday, the Singapore Exchange (SGC) said that "in the January to March quarter, we referred nine cases to MAS of which three were related to insider trading and six to market manipulation", Bloomberg reported.

MAS and CAD raided at least four broking houses on Monday, including DBS Vickers, Maybank Kim Eng, OCBC Securities and Philip Securities, the Business Times reported earlier on Friday.

White collar investigators had visited these offices to take people in for question along with other items, the report said.

"The Monetary Authority of Singapore and the Commercial Affairs Department of the Singapore Police Force are jointly investigating possible contraventions of the Securities and Futures Act (Cap. 289) and have obtained documents and items from several broking firms and trading representatives. As investigations are ongoing, we are not able to provide further information" said an MAS spokesman on Friday.

Among other things, the Securities and Futures Act governs institutions' and individuals' activities in the public markets.

One trader believes that the authorities are stepping up monitoring and enforcement following the October 2013 penny stock crash.

"In recent months there were a number of counters collapsing spectacularly and obviously people have gotten hurt," he said, declining to be named.

"In most cases the underlying company fundamentals have changed little. This is perhaps suggesting that the counters have been played up."