Tokyo Gas Co. said Tuesday that the Mizuho financial group knew it was having problems integrating the computer systems of its three component banks before the April 1 merger.

Tokyo Gas officials said that in late March a test in which data from the utility's large-lot customers were sent to Mizuho's integrated computer system ended in failure.

Mizuho, however, denied that such a test had been conducted, though it admitted to receiving client data from Tokyo Gas in mid-March.