Vietnam has launched an investigation into the website of the tour organizer for K-pop group Blackpink ahead of a show in Hanoi after fans claimed it showed a map including disputed boundaries in the South China Sea. Vietnam’s Culture Ministry on Wednesday announced the probe “to verify the suspicion that the company organizing the Blackpink music night promoted the cow-tongue line,” using the local term referring to the “nine-dash line.” The controversial line indicates China’s claim to almost all of the South China Sea—a claim which has been ruled to have no basis in international law. The row involving Blackpink, who are set to perform in Vietnam for the first time at the end of July, comes after Vietnam banned the upcoming Barbie movie from being shown in the country over a scene featuring a map including the nine-dash line.