SEOUL, South Korea (AFP) — South Korean police raided the Starbucks national headquarters Wednesday, the chain’s local operator told Agence France-Presse (AFP), following allegations an advertising campaign defamed activists slain in 1980 pro-democracy protests.

Starbucks Korea caused an uproar this year when it launched a “Tank Day” promotion on 18 May, touting a new line of capacious tumblers for its coffee beverages.

The date marked the anniversary of the 1980 Gwangju pro-democracy uprising, when at least 165 civilians were killed as a military dictatorship rolled tanks out onto the streets.

The chain was accused of trivializing the nation’s landmark protest movement and insulting the dead, remembered as martyrs by many South Koreans.

A civic group and bereaved families filed a complaint accusing members of the Shinsegae Group, which operates Starbucks Korea, of defaming and insulting the victims and relatives.

“The Seoul police raided the headquarters of Starbucks Korea this morning as part of the ongoing investigation,” a Shinsegae Group spokesperson told AFP, declining to provide further details.

Seoul police said an investigation into the firm was ongoing, but also declined to provide further information about the case.

The complaint named Shinsegae Group chairman Chung Yong-jin and Son Jung-hyun — the former CEO of Starbucks Korea, who resigned over the furor.