TOKYO, Japan (Reuters) -- Shares in Sony Corp. fell to a 2 month low on Monday after Toshiba Corp. and Fujitsu Ltd. joined the list of PC makers recalling Sony-made batteries, boosting the potential blow to its earnings.

Macquarie Research estimates the recall could cost Sony up to 40 billion yen ($339 million), higher than Sony's previous estimate of 20 to 30 billion yen when the recall involved only PCs made by Apple Computer Inc. and Dell Inc.

Sony's stock was down 2.3 percent at 4,670 yen as of 0425 GMT, underperforming a 1 percent rise in the benchmark Nikkei average. Sony dropped as low as 4,620 yen in early morning trade, a level last seen in mid-July.

Triggering the fall was an announcement by Toshiba on Friday that it would recall 830,000 laptop computer batteries, which Sony has said can short circuit on rare occasions, overheat and catch fire. Fujitsu also said it would join the recall but did not give the number of units to be replaced.

That announcement came one day after International Business Machines Corp. and Lenovo Group Ltd. said they would recall more than half a million batteries made by Sony after a PC caught fire at Los Angeles International Airport.

August recall

Dell and Apple kicked off the saga in August by recalling nearly 6 million Sony-made batteries. At that time, Sony put the cost at 20-30 billion yen and said it did not anticipate any further recalls, a prediction that proved to be untrue.

David Gibson, an analyst at Macquarie Research in Tokyo, said the cost could now expand to 33 to 40 billion yen assuming a total of 10 million batteries, although the cost could end up being less than 15 billion yen if the actual recall rate is low.

"However the public relations disaster may put into question the 14 billion yen in annual OP (operating profit) coming from the battery division," Gibson wrote in a note to clients.

Sony is forecasting a group operating profit of 130 billion yen for the current business year to March.

Sony launched a global replacement program for its batteries in the wake of the Lenovo recall. It said the costs of the program were not clear at present because details including exactly how many batteries have to be replaced are not yet set.

Sony spokesman Takashi Uehara said on Monday that the company planned to announce more details on the program once they become clear. He would not comment on the potential cost.

This is the latest setback to shake consumer confidence in Sony's reputation as a manufacturer. Last month Sony also delayed the European launch of its new game console, the PlayStation 3, by four months to March due to a production glitch.

Sony shares have lost a little over 10 percent since Dell's initial announcement in August, while the Nikkei has gained about 3 percent.

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