The authorities appear to be zooming in on Edge Media Group owner Tong Kooi Ong following the arrest of its chief executive officer (CEO) Ho Kay Tat last month.

Ho was detained overnight together with three senior editors from The Malaysian Insider and the news portal's CEO Jahabar Sadiq late last month. The Malaysian Insider is owned by the Edge Media Group.

Malaysiakini learnt that Tong ( left ) is now being investigated by the Inland Revenue Board (IRB) for possible tax violations.

Sources also revealed that IRB officers carried out a raid, but did not specify where it took place.

The sources also claimed that the investigation could be "politically motived" as both The Edge and The Malaysian Insider had published a series of damaging articles on 1Malaysia Development Bhd (1MDB).

"This is an abuse of process by the IRB to break Tong financially, just like how the police arrested the editors last month," said a source familiar with the matter.

Contacted later, an IRB spokesperson declined to comment, saying they are not allowed to discuss cases that are being investigated.

Auditing firm Price Waterhouse Coopers, which is appointed by Tong, was also tightlipped on the matter.

In late January, several blogs accused Tong of being responsible for ringgit speculation, leading to the decline of the currency, which prompted the tycoon to threaten legal action.

In February, Tong served a legal notice on business tycoon Jho Low, who is linked to the quagmire in 1MDB.

Tong claimed that Low is behind the attacks against him and his media organisations.

Meanwhile, the TMI bosses and The Edge group CEO were detained over an erroneous article published in the news portal on the Conference of Rulers rejecting the proposal to amend the Federal Constitution to implement hudud.

Their detention drew widespread condemnation. Jahabar himself alluded that the authorities had an ulterior motive .

Even former prime minister Dr Mahathir Mohamad, a staunch critic of 1MDB, and DAP veteran Lim Kit Siang found themselves on the same page on this issue.

Lim went on to caution the authorities against using the hudud article in TMI as an excuse to go on a fishing expedition on the source behind the 1MDB reports.

These reports have bruised Najib's reputation, forcing the prime minister to instruct the auditor-general to audit the 1MDB.

Though he promised stern action if any wrongdoings are detected, detractors have dismissed the probe as nothing more than an eyewash.