A combination photo shows three former Tokyo Electric Power (Tepco) executives Tsunehisa Katsumata (L), then TEPCO chairman, and two former vice presidents Ichiro Takekuro (C) and Sakae Muto in this undated photo taken by Kyodo and relased by Kyodo on February 29, 2016.[Photo/Agencies]

TOKYO  -- Three of Tokyo Electric Power Company's (TEPCO) former executives were indicted on Monday on charges of professional negligence for their failure to take the appropriate measures that could have prevented the nuclear disaster at the Fukushima Daichi nuclear power plant in 2011.

The arraignments of the top executives include charges that their negligence, following a huge earthquake-triggered tsunami knocking out the key cooling functions of reactors at the nuclear plant in Japan's northeast on March, 11, 2011, resulted in both injury and death.

The officials have been named as Tsunehisa Katsumata, 75, who was chairman of TEPCO at the time of the disaster, and Sakae Muto, 65 and Ichiro Takekuro, 69, who served as the now-embattled utility's vice presidents.

The indictments follow revelations earlier this week that TEPCO had knowledge of multiple meltdowns at the plant's reactors following the tsunami hitting, but intentionally refrained from informing the public of the fact until months later. TEPCO, owner and operator of the six-reactor facility, also fired a communications representative who had suggested that a meltdown of a reactors core may have happened at the time.

The trail of the trio follows a probe by the Tokyo District Prosecutors Office into the matter, after an independent citizen's panel adjudged the executives should be charged for their negligence in the summer of 2014.

The committee found that the executives in questions knew as early as July 2009 that the nuclear plant, located on the Pacific coast in the prefecture, could possibly be hit by an earthquake-triggered tsunami of more than 15-meters high -- such as the one that inundated the plant two years later -- yet did nothing to take preemptive, preventative measures to fortify the facility.

Those with knowledge of the case said Monday that the trial may not start this year, however, as collecting the necessary information, evidence, and overall preparations for the proceedings will be a lengthy process, with the defendants also likely to plead not guilty to the charges.

The panel judged that the executives' dereliction of duty led to the injuries of 13 people and the deaths of 44 people who died in hospital after being evacuated from the plant following the worst commercial nuclear disaster in history.

TEPCO is still grappling with the fallout from the disaster and since 2011 has seen numerous incidents of radioactive leaks at the plant, many of which saw contaminated water flow directly into the Pacific, much to the consternation of the international community.

The latest estimates following surveys at the troubled plant have concluded that some 600,000 tons of radioactive water are still being contained in storage tanks at the plant, some which have overflowed during heavy rain, others of which have sprung leaks with water mixing with radioactive materials in drainage ditches, which connect to the ocean, under the ruptured reactor buildings.