US officials voiced concern about a lack of information after Japan’s Fukushima nuclear disaster and issued a controversial warning not to go near the plant after intense discussions, transcripts showed.

Transcripts of the Nuclear Regulatory Commission, released ahead of the one-year anniversary of the crisis, showed that US officials at times relied on information from the media as Japan initially declined assistance.

“We’re getting various information from various sources, most of which is either conflicting or supporting the little bit of information that we actually have,” said Martin Virgilio, a senior official in charge of nuclear safety shortly after the March 11 tsunami smashed into Fukushima.

Nuclear officials debated at length over a decision to urge Americans to stay out of the 80-kilometre radius around the Fukushima Daiichi plant, a wider no-go zone than that put in place by Japanese authorities.

“If this happened in the US, we would go out to 80km. That would be our evacuation recommendation,” Bill Borchardt, the commission’s executive director for operations, said in the transcripts.

The transcripts showed that the commission considered a larger evacuation if the situation deteriorated or the wind changed direction. Several European countries issued dire warnings and urged residents to leave Tokyo.

The no-go zone advice came as Nuclear Regulatory Commission’s chairman, Gregory Jaczko, told a congressional committee on March 16 that Reactor No. 4’s pool for spent fuel had dried, meaning its ability to keep cool was severely diminished and radiation would spike.

That assessment turned out to be inaccurate. The transcripts showed Mr Jaczko had discussed the spent fuel pool with aides, knowing that he would be asked the question during his appearance on Capitol Hill.

“I’m going to say (the assessment) is from a team that is in Japan that is embedded that is working closely with the Japanese utility and the Japanese regulatory agency, is that correct?” Mr Jaczko asked.

Senior officials replied in the affirmative, although one staff member –apparently speaking when Mr Jaczko was no longer on the conference call – disputed the assessment.

Last year’s earthquake set off a tsunami that left more than 19,000 people dead in Japan’s worst post-World War II disaster. While the disaster crippled the Fukushima plant, the nuclear crisis has not directly claimed lives.