Spain's Bankia, taken over by the state because of its troubled loan portfolio, plummeted on the stock market today after an audit raised questions over its 2011 results.

The bank, created in 2010 from a merger of seven savings banks, plunged 8.27% to 1.708 euros in the morning, meaning it has lost more than half of its value since its listing at 3.75 euros on July 20 last year.

The price slump brought losses in Bankia stock so far this month to 34.1%.

Bankia sent a statement to the stock market regulator, CNMV, giving its provisional results for the first quarter of 2012 but without its net profit or the level of provisions made against bad loans.

Complete information "will be given once we have the definitive annual accounts for 2011 and the audit report on them," the bank said.

The audit could lead to "variations" in the level of provisions needed in the first quarter of 2012, it said.

Bankia had the industry's largest exposure to the property market at €37.5 billion at the end of 2011, of which €31.8 billion were classed as problematic.

Spain is taking a controlling 45% stake in Bankia by nationalising its parent group Banco Financiero de Ahorros (BFA).

Bankia announced last week it would set aside €4.7 billion - by far the highest among Spain's banks - in case healthy loans to the property sector go bad, in line with a sweeping government reform.