BERLIN (AP) — Shares in German payment service provider Wirecard AG plunged Thursday as the company announced it was postponing its delayed annual report yet again.

Wirecard’s stock price plummeted by 50% on the Frankfurt exchange after the Munich-based company said it was informed by auditors that an escrow account containing 1.9 billion euros ($2.14 billion) didn’t have the necessary certificate.

Chief executive Markus Braun said it was “currently unclear whether fraudulent transactions to the detriment of Wirecard AG have occurred.”

“Wirecard AG will file a complaint against unknown persons,” he added.

Once seen as a stellar example of Germany’s tech industry, Wirecard has been battered by allegations of financial irregularity in recent years. The company has hit back by claiming that its share price was being intentionally manipulated by speculators.