(Telecompaper) Chinese regulators have launched an investigation into memory-chip makers US-based Micron Technology, South Korea's Samsung Electronics and SK Hynix. The three companies report that State Administration for Market Regulation officials have recently visited their offices in China. The regulator did not comment on the matter, Reuters reports. Micron, Samsung, and SK Hynix, the dominant suppliers of DRAM chips, said they are cooperating with the investigators, but did not release any details about what the probe is about.