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Feb 21 (Reuters) - French construction materials group Saint-Gobain SGOB.PA is in initial talks to acquire Australian building materials firm CSR Ltd (CSR) , Bloomberg News reported on Wednesday.

The companies are working with advisers to narrow down on a deal, the report said, citing people familiar with the matter, with one of them adding that St. Gobain has lined up financing for a potential transaction.

CSR shares rose about 17.4% on Wednesday and were halted for trading. It had a market value of A$3.23 billion ($2.12 billion), as of last close, according to LSEG data.

CSR and Saint Gobain did not immediately respond to Reuters' request for comment.

($1 = 1.5235 Australian dollars)