The Bank of Japan said it will tighten control of information about policy decisions after questions were raised about a possible leak of officials' discussions just before last month's announcement of negative interest rates.

The central bank will limit the use of communication devices during meetings and request assistance from government representatives for tighter information control at policy gatherings, the BOJ said in an email statement Wednesday.

The central bank did not find evidence of a leak of information from its Jan. 29 discussions, it said, after reviewing security camera footage and investigating workers, executives and related government officials.