South Korean chipmaker Hynix is investigating how two of its memory chips ended up inside Huawei’s Mate 60 Pro, a controversial smartphone launched last week.

In the wake of TechInsights’ analysis of the Huawei handset, which took the phone apart for analysis, two of Hynix’s products, a 12 gigabyte (GB) LPDDR5 chip and 512 GB NAND flash memory chip, were found inside it. Hynix’s shares fell more than 4% on Friday.

According to G Dan Hutcheson, vice chair of TechInsights, the development is significant because there are restrictions on what SK Hynix can ship to China. Why are these chips so expensive? Where do they come from? There is a big question as to whether any laws were violated.”

The Hynix spokesperson said the company was aware its chips were used in the Huawei phone and was investigating the matter.

As a result of US restrictions against Huawei, the company “no longer does business with Huawei.”

“SK Hynix strictly complies with the export restrictions imposed by the US government,” the company said.

The memory chips may have been purchased from the secondary market rather than directly from the manufacturer, according to industry insiders. The US export curbs may have also led Huawei to accumulate a stockpile of components before they were fully implemented.