Japanese prosecutors will likely decide again not to indict three former Tokyo Electric Power Co executives over their handling of the 2011 Fukushima nuclear disaster, media reported on Friday, but a rarely used citizen's panel could still force an indictment.

The Tokyo District Prosecutors Office has been reinvestigating the case after a citizens' panel ruled in July that three former Tepco executives, including then-chairman Tsunehisa Katsumata, should be indicted over their handling of the world's worst nuclear disaster since Chernobyl in 1986.

The prosecutors are likely to finalize their decision not to issue indictments early next year because of insufficient evidence, the Yomiuri newspaper and Kyodo news agency said.

An official with the prosecutors office said no decisions had been made yet.

If the prosecutors again decline to take up the case, as some experts expect, the 11-member panel of unidentified citizens can force an indictment by court-appointed lawyers if eight members of the panel vote in favor.

Prosecutors last year declined to charge more than 30 Tepco and government officials who had been accused by residents of ignoring the risks of natural disasters and failing to respond appropriately when the crisis struck.

After a review of evidence, the citizens' panel ruled that three of them - Katsumata and former executive vice presidents Sakae Muto and Ichiro Takekuro - failed to protect the Fukushima Daiichi nuclear plant despite warnings it faced big tsunamis.

Prosecutorial Review Commissions, made up of citizen appointees, are a rarely used but high-profile feature of Japan's legal system introduced after World War Two to curb bureaucratic over-reach.