An outside investigation team appointed by the operator of Japan's damaged Fukushima nuclear plant said Thursday that an instruction from then-company president to avoid mentioning "meltdown" delayed disclosure of the status of three reactors.

Tokyo Electric Power Co. described the Fukushima reactors' condition as less serious "core damage" for two months after the March 2011 earthquake and tsunami wrecked the plant.

The panel of three TEPCO-commissioned lawyers said TEPCO used the milder expression despite knowing the damage far exceeded its meaning, following an instruction by then-president Masataka Shimizu. The investigation, however, found that TEPCO's delayed acknowledgement broke any law.

In the 70-page report, the lawyers said Shimizu instructed his deputy not to use the word "meltdown" during news conferences immediately after the crisis when officials were peppered with questions about the reactor conditions. At the very beginning, TEPCO's vice president at the time, Sakae Muto, had mentioned a "possibility of a meltdown" until March 14, 2011.

Video footage of a news conference that day shows a company official rushing over to Muto when he was about to respond to a question about conditions of the reactors, showing him a memo and hissing into his ear: "The Prime Minister's Office says never to use this word, never."

Yasuhisa Tanaka, lawyer who headed the investigation, said interviews of 70 former and current TEPCO officials, including Muto, showed that Muto had planned to use the word "meltdown" until he saw the memo. The memo containing Shimizu's instruction was never found, however, Tanaka said.

Government and parliamentary investigations have suggested officials, seeking to play down the severity of the crisis, showed reluctance in using the term. Tanaka said his investigation, which did not interview government officials, could not establish if or what exactly Shimizu was told by the Prime Minister's Office.

TEPCO said the damage involved 25 to 55 percent of the fuel but avoided saying "meltdown" despite knowledge and computer simulation of that occurrence.

TEPCO earlier this year acknowledged an existing internal manual was overlooked.