Frankfurt am Main — Shares in German payments processing firm Wirecard plunged Tuesday after the Financial Times (FT) published new documents alleging accounting irregularities.

By 8am GMT in Frankfurt, the shares were down 15.6%, at €118.15, making up some of the losses suffered immediately after the report’s publication.

Lawyers for Wirecard told the FT that the company “does not believe the document to be authentic” on which much of the reporting was based.

Wirecard’s shares have seen a roller-coaster ride this year.

German authorities, earlier this year, said they would investigate the FT after “fintech” rising star Wirecard denied its previous reports that the firm was cooking the books, which sent the group’s stock tumbling 40% — or €9bn — in a few weeks.

However, on Tuesday, the FT published internal communications and financial reports it said contain “strong indications” that hundreds of millions of euros of payments processed for some Wirecard clients “could not have taken place”.

The FT’s probe focused on a Dubai-based payments processing company called Al-Alam. While Wirecard documents show Al-Alam accounted for about half the group’s profits in 2016, processing about €350m of payments per month in 2016/2017 for 34 major clients, the FT said it could not confirm any of those client relationships.

Of 15 clients they reached, just four told the FT they did use Wirecard directly for payments processing, rather than go through Al-Alam. Others did not respond, could not be tracked down, or had long since been shuttered.

The FT said its “findings cast doubt on whether substantial sales and profits were actually travelling through Al-Alam to Wirecard — or were simply invented”.

In February, German financial markets watchdog Bafin ordered a ban on“short-selling or betting against Wirecard shares after wild stock price moves following FT allegations of padding the books in its Singapore office.

The same month, Munich prosecutors said they were investigating an FT journalist over the reports, and in March Bafin filed charges against unnamed people over alleged market manipulation to undermine Wirecard’s share price.

While Wirecard published a report from Singapore-based law firm Rajah & Tann it said cleared up allegations of accounting irregularities, the FT has always stood by its reporting, publishing a legal report it had commissioned that found no wrongdoing by the journalist behind the articles.

In relation to Tuesday’s article, Al-Alam told the paper that it “was not involved in any alleged process to fake revenues or profits”.

Wirecard has long been seen as a figurehead for “fintech” companies that are up-ending the traditional world of banking and payments. Founded in 1999, massive growth in the electronic payments it guarantees in exchange for a commission has helped shoot it into the blue-chip DAX 30 index.