TOKYO -- Three former Japanese utility executives have been formally charged for alleged negligence in the Fukushima nuclear disaster, becoming the first ones from the company to go to criminal court.

National broadcaster NHK reported that a group of court-appointed lawyers on Monday indicted Tsunehisa Katsumata, chairman of Tokyo Electric power Co. at the time of the crisis, along with two other TEPCO executives. The three men, charged with professional negligence, were not arrested.

The indictment follows a decision by an 11-member judicial committee in July to send the three men to criminal court after prosecutors had dropped the case.

Experts say it may be difficult to prove criminal responsibility for failing to prevent the Fukushima meltdowns, but many people including the residents affected by the disaster say they hope that any trial would reveal more facts about the disaster and TEPCO's role that the utility has not disclosed.

The committee said in July that the three men neglected to take sufficient measures even though they were aware of the risk of a tsunami at the Fukushima plant. It said they should be charged with professional negligence resulting in death and injury during the accident and its aftermath, including the deaths of dozens of senior citizens in a hospital who died during and after the lengthy evacuation.

The Tokyo District Court has since selected a team of five lawyers to act as prosecutors to formally press charges in court.

Three reactors at the Fukushima Dai-ichi plant damaged in the March 2011 earthquake and tsunami suffered meltdowns, triggering massive radiation leaks that forced tens of thousands of people to evacuate.

Government and parliamentary investigative reports have said TEPCO's lack of a safety culture and weak risk management, including an underestimate of tsunami threats, led to the disaster. They said TEPCO ignored tsunami safety measures amid collusion with then-regulators and lax oversight.

TEPCO has said it could have been more proactive on safety measures, but that a tsunami of the magnitude that crippled the plant could not be anticipated.

While struggling with a cleanup at the wrecked Fukushima plant that will take decades, TEPCO is hoping to restart two reactors at the Kashiwazaki-Kariwa plant in northern Japan.

The disaster resulted in Japan taking all of its nuclear power reactors offline for checks. Of the 43 workable reactors in Japan, three have been put back online since last year, while the remaining are still offline for repairs or safety checks.