Late last month, the construction arm of South Korea's top steelmaker said an independent audit within the company found two of its executives and about a dozen workers operated a slush fund worth about 10 billion won ($8.8 million) in Vietnam.
  

Prosecutors launched their own investigation last week, raiding the head office of POSCO E&C for computer hard disks and documents related to these allegations.    
   

The Seoul Central District Prosecutors' Office investigating the case said it started calling executives in from Sunday for questioning over their suspected involvement.
  

An executive surnamed Park, who was the chief of POSCO E&C's Vietnamese operations, is among the first officials to face questioning, prosecutors said. Others include officials who were directly involved in the running of POSCO E&C's Vietnam branch.
  

Prosecutors said they are mainly focused on determining how the firm was able to leave millions of dollars out of its books.
  

POSCO E&C says it exaggerated its payments to local subcontractors, which were later reimbursed from 2009 to 2012. But authorities believe some of the funds may have been sent back to South Korea.
  

Prosecutors also plan to interrogate former POSCO E&C Vice Chairman Chung Dong-hwa, who ran the firm during the cited period.
  

But first, they will focus on uncovering the exact size and use of the slush funds before calling in the higher-ups.
  

Some sources within the prosecution said former POSCO Chairman Chung Joon-yang has been banned from leaving the country to possibly face questioning.
  

Prosecutors also did not rule out the possibility of expanding the probe to other POSCO affiliates either, one of which was found to have evaded taxes in 2013. The National Tax Service referred the case to the prosecution last year, though POSCO E&C says the corruption was limited to a few individuals within the company.
  

Last week, Prime Minister Lee Wan-koo declared an all-out war on corruption, which analysts say seems to be aimed at propping up weak public support for President Park Geun-hye's job performance by launching an anti-graft drive against government officials and businessmen, especially those who worked for the previous Lee Myung-bak administration. (Yonhap)