* Says not negotiating any concrete deal with shareholders
* Colonial shares up 9.1 percent to 0.982 euro (Recasts with comment from Grupo Villar Mir)
MADRID Feb 25 (Reuters) - Family-owned Spanish group Villar Mir said it was looking at assets owned by Colonial, after a report that it was studying a bid for the loss-making real estate firm's commercial property business.
Colonial had nearly 3.5 billion euros ($4.6 billion) debt as of September, and assets worth 5.2 billion euros. It is 90 percent-owned by former creditors after a debt-for-equity swap.
News website El Confidencial reported on Monday that Villar Mir - controlled by the owner and chairman of Spanish builder OHL - was studying a bid for Colonial's commercial property business.
"Grupo Villar Mir has been studying a deal involving Colonial ... but any possible deal would not have any direct or indirect impact on OHL," it said on Monday.
Colonial, with a market capitalisation of about 200 million euros, has spun off toxic property assets into Asentia, a new unit created in 2011, and kept hold of healthier parts of its business.
Dozens of property firm have collapsed in Spain after a property bubble burst and as house prices fell around 40 percent from their 2007 peak.
While Colonial has said it expected to begin refinancing talks with creditors soon on debt that comes due in 2014, banks have become more reluctant to refinance property debt, with no recovery of the battered market in sight.
Colonial declined to comment on the El Confidencial report.
Its shares were up 8.9 percent at 0.98 euro at 1255 GMT. ($1 = 0.7598 euro) (Reporting by Tracy Rucinski and Tomas Cobos; Editing by Dan Lalor)