Hard to find an English speaking source for it (we know how friendly the UK and Russian governments are lately), but for example, here https://www.nzz.ch/wirtsc

Hard to find an English speaking source for it (we know how friendly the UK and Russian governments are lately), but for example, here https://www.nzz.ch/wirtschaft/wirecard-jan-marsaleks-spuren-in-russland-ld.1569026 https://www.nzz.ch/wirtschaft/wirecard-jan-marsaleks-spuren-... are claims that Marsalek himself admitted relations with the FSB.