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Wirecard last year supplanted German lender Commerzbank on the blue-chip DAX index.
Shares of German payments firm Wirecard have suffered big losses in less than two weeks.
The company drew investor attention last year when its market capitalization climbed above that of Deutsche Bank.
It also made waves after the firm joined the domestic blue-chip DAX index, ousting Commerzbank.
But since Jan. 30, Wirecard's stock price has dropped almost 30 percent amid developing reports of an accounting scandal at its Singapore office.
CNBC explains what you need to know about the accusations facing Wirecard.
FT investigation
Wirecard's troubles appeared to start after a Jan. 30 report by the Financial Times said a senior executive at the company used forged and backdated contracts, possibly to inflate revenue.
The newspaper, which cited a whistleblower and internal documents, said Edo Kurniawan, who runs the firm's Asia-Pacific accounting and finance operations, ordered potentially fraudulent transactions.
The report said a document showed how 37 million euros ($42 million) moved in and out of Wirecard's subsidiaries and external businesses across seven sets of complex transactions flagged as suspicious.
It also describes a practice called "round-tripping," which is where a series of potentially dubious transactions are made across borders to various units, with the apparent aim of making such transactions look legitimate to local auditors.
One example the FT cites entails money changing hands between Wirecard's operations in Hong Kong and Singapore and two of its subsidiaries in India.
The allegations appear to have dented the image of a company which has not previously attracted public scrutiny, typically processing digital payments of roughly 250,000 merchants.
The company denied any wrongdoing. It said at the time that it had "stringent internal and external audits" and that any concerns over its accounting practices are "always thoroughly and appropriately investigated."
Second FT report
A further report by the FT, published Feb. 1, claimed that an external law firm hired by Wirecard found evidence indicating "serious offences of forgery and/or of falsification of accounts" at its Singapore office.
According to the paper, the law firm, Rajah & Tann, was given a mandate on May last year to conduct an independent probe into the affair.
Wirecard rebutted the story at the time as "inaccurate, misleading and defamatory." The article nonetheless put significant pressure on Wirecard's share price, sending it down almost 30 percent on the day.
On Feb. 4, Wirecard said that it had hired the aforementioned law firm to review accounting practices at its Singapore office following allegations brought forward by an employee, but that the investigation had so far found no findings of criminal misconduct.
Wirecard threatens legal action against FT
A third report by the FT, published on Feb. 7, said that two senior officials at Wirecard's Munich head office — head of treasury Thorsten Holten and head of accounting Stephan von Erffa — were aware of the alleged round-tripping scheme.
The financial media outlet described a pattern of "book-padding" across the Munich-based firm's Asian operations over several years. Wirecard denied the report.
The company went on the offensive the following day, threatening legal action against the FT over what it called "unproven and false allegations" against its employees.
"Wirecard is taking legal actions against FT and its unethical reporting," the firm said in a Feb. 8 statement. Its share price initially jumped following the defensive comments.
Shortly after the release of that statement, police in Singapore said they had "raided the premises of the Wirecard entities in Singapore," news that sent the company's stock down once again.
Subsequently, Munich's state prosecutor said it was aware of the search of Wirecard's offices in Singapore, but that it still saw no sufficient reason to launch a criminal probe against the company's managers.
Shares of the company hit a one-year low that day.
Wirecard was not immediately available for comment on this story when contacted by CNBC.
