The president of Tokyo Electric Power Co. during the Fukushima nuclear crisis told employees not to publicly use the term “meltdown,” apparently in response to government pressure, a third party report released Thursday said.

The report, compiled by three lawyers, said it is highly likely the government at the time pressured Masataka Shimizu, then Tepco’s president when the monstrous earthquake and tsunami disabled the Fukushima No. 1 nuclear power plant on March 11, 2011, about the utility’s disclosures in the early stages of the crisis.

The report said someone in the government, then headed by Prime Minister Naoto Kan of the Democratic Party of Japan, was unhappy Tepco had revealed a photo of the blown-up building for reactor No. 1 on March 12 without telling the government in advance.

The Prime Minister’s Office then called Shimizu the same day. After Shimizu returned to Tepco’s Tokyo headquarters, he told his fellow executives that they needed to check with the Prime Minister’s Office whenever disclosing information to the public, according to the report.

The report also said Shimizu sent a note on March 14 to Vice President Sakae Muto, who was overseeing the plant and holding a news conference, to warn him not to say meltdown.

“Considering this fact, it is presumable that the Prime Minister’s Office requested Shimizu to be careful about admitting to a meltdown in public,” the report said.

The panel thought this was a critical point that required further investigation but was unable to track down a specific bureaucrat who made such a request. Yasuhisa Tanaka, who headed the panel, said it conducted hearings with 60 Tepco employees but did not talk to anyone from the government side.

Tepco did not acknowledge that a reactor meltdown had occurred until May 15, 2011 — two months after the fact.

Asked whether Tepco was intentionally covering up the meltdowns, Tanaka said that was probably not the utility’s intention at the time.

“Looking at the situation back then, we think it was difficult for Tepco to use the term meltdown because even the Nuclear and Industrial Safety Agency couldn’t use it” due to apparent government pressure, Tanaka said.

The Nuclear and Industrial Safety Agency was Japan’s nuclear watchdog at that time.

The panel spent about three months investigating why Tepco could not publicly reveal the meltdowns occurred earlier than it did.

In February, nearly five years after the crisis, Tepco announced it should have declared the meltdowns earlier, citing the existence of a company manual that listed what constitutes a meltdown. The manual says that meltdown is a state in which 5 percent or more of the fuel rods is damaged.

As of March 14, 2011, Tepco estimated that 55 percent of the fuel rod assemblies in reactor No. 1 and 25 percent of those in reactor No. 3 were damaged but did not declare that they had melted until May that year.

Niigata Prefecture has been pressuring Tepco to look into why it took about two months for the utility to admit to a meltdown.

Niigata hosts Tepco’s Kashiwazaki-Kariwa nuclear plant, which the firm desperately wants to restart, but Niigata Gov. Hirohiko Izumida has stressed that he won’t give the green light until the Fukushima crisis has been thoroughly investigated.

Tepco had explained to Niigata that it did not use the term meltdown because there was no clear definition of it. But it found the manual in February, which contradicted the explanation and led to the third-party investigation.

The report said that workers at the Fukushima plant were apparently following the manual but seemed to avoid using the term meltdown, presumably because there was a common understanding within the company not to use it.

Tokyo Electric changed its name in April to Tokyo Electric Power Company Holdings Inc.