Luxembourg said Tuesday it would place two key shareholders of struggling Portuguese lender Banco Espirito Santo (BES) in administration after they demanded protection from creditors.
A court said it had accepted the request by Rioforte Investments and Espirito Santo Financial Group (ESFG) and appointed an official to oversee their affairs.
ESFG is the single biggest shareholder in BES with a more than 20 percent stake.
A third BES holding company, Espirito Santo International (ESI), was put under adminstration in Luxembourg last week.
Shares in BES closed the day down 10.60 percent at 0.3880 euros in Lisbon after the news.
BES is the biggest private bank in Portugal, operating in several sectors of the economy, stoking concern that its problems could have a wider knock-on effect.
Late on Monday, the Portuguese central bank said that BES could withstand a blow to its accounts, even if its half-year losses exceed its financial reserves estimated at 2.1 billion euros ($2.8 billion).
The central bank also said it could intervene if necessary, with reserves of 6.4 billion euros available out of 12 billion euros provided by the European Union and International Monetary Fund under its now completed bailout.
The Expresso newspaper said the bank could report a loss of 3.0 billion euros because it had greater-than-expected exposure to the Espirito Santo group of companies.
BES on Tuesday in a statement cancelled a shareholder meeting scheduled for July 31 that was due to approve its interim results at the request of ESFG and major shareholder Credit Agricole.
Administration allows a company to put its affairs in order while being protected from creditor claims.
An administered company may eventually be closed down, restructured as a completely new entity or broken up and sold off.
The difficulties in the Espirito Santo group of companies surfaced earlier this year, denting confidence in Portugal's future after it exited a 78 billion euro EU-IMF debt rescue programme.
Last week, former BES head Ricardo Salgado was arrested in connection with money laundering following a massive probe dating back to 2011.
The investigation targets tax evasion and money laundering relating to private wealth managers in Switzerland and clients in Portugal.
He was forced out as head of BES after 23 years on June 20 amid allegations of accounting irregularities at one of the bank's Luxembourg-based holding companies.