The Wirecard headquarters in Munich and four properties in Austria and Germany were raided by police and public prosecutors on Wednesday as they extended their probe into the credit card operator's business that collapsed last week.

Wirecard filed for insolvency owing nearly $4 billion to lenders after revealing a €1.9 billion ($2.1 billion) anomaly in its finances that its auditor EY claimed was the product of a well-organized multinational fraud.

The investigation has already ensnared former Wirecard chief executive officer Markus Braun, who was apprehended last week and later on freed on 5 million-euro bail and released from custody.

Authorities are also targeting top management board executives Susanne Steidl and Alexander von Knoop, including former chief operating officer Jan Marsalek, a spokesperson for Munich prosecutors disclosed. German authorities have issued a warrant of arrest for Marsalek, who was last believed to have traveled to the Philippines.

Braun had stepped down as CEO days earlier, moments after the German payments group said auditors could not locate the accounts in the Philippines supposedly containing the missing $2.1 billion. His arrest came hours after Wirecard claimed that the funds may not have existed in the first place.

Investors wiped out a huge volume of the company's stock value in the last two weeks, and executives on Thursday said Wirecard was filing for bankruptcy protection. Authorities had already conducted a search of the company's office earlier last month. At the time, the prosecutor's office had carried out proceedings against the four ex-members of Wirecard's management board.

Shares of Wirecard plunged as much as 17 percent around noon on Wednesday after an exchange technical glitch was resolved in Frankfurt. The stock dropped around 95 percent in the two weeks since Wirecard acknowledged the missing billions.

The collapse of a financial technology giant once hailed as one of the most lucrative investments in Europe has set the stage for political accusations in Germany and a new probe into possible financial machinations from the Philippines to Mauritius.

Meanwhile, assets of the scandal-hit German firm are gaining interest from several prominent investors and a sale process involving investment lenders is being worked upon, Wirecard's initial insolvency administrator stated.

Worldline, a French payments firm, is one of the groups interested in acquiring portions of Wirecard, according to German publication Frankfurter Allgemeine Zeitung last week. The North American unit of Wirecard is seeking an acquisition agreement with interested parties, with an investment bank assisting in the sale transaction.