Seoul, South Korea (CNN) -- South Korea is asking some companies to stop signing trade deals with North Korea, as tensions over the sinking of a South Korean warship continue, South Korean media reported Thursday.
Government officials are asking companies that send raw materials to North Korea for processing to stop dealing with the North, Yonhap news agency reported.
However, the new measure does not apply to more than 100 South Korean companies that operate in the North Korean border town of Kaesong, Yonhap reported. Those companies employ about 42,000 North Korean workers, the agency reported.
The new measures come as South Korea investigates the mysterious March 26 sinking of a warship.
Fifty-eight men escaped the sinking ship. Forty of the 104 crew members have been confirmed dead, and six more are believed dead, though they are still listed as missing.
A team of South Korean military and civilian investigators tentatively concluded last month that an explosion at close range, and not a direct hit, sank the 1,200-ton ship. A U.S. military official also said last month that he believes a North Korean torpedo attack was the most likely cause for the sinking.