DoCoMo said it has sold about 4,000 high-end Bold phones, and about 30 users have complained the phone's keyboard area had heated up. The company said it has received no reports of users getting burned or of phones catching on fire.
"This issue appears to be specifically limited to the BlackBerry Bold devices sold in Japan since last week and sales of BlackBerry Bold devices in other countries are unaffected by this matter," RIM said in a statement.
RIM said it had ruled out a battery problem, but said the root cause is still being investigated.
NTT DoCoMo began selling the product in Japan last week and the companies hope to renew sales in Japan soon, RIM said.