TOKYO (AP) — The Japanese government’s worst-case scenario at the height of the nuclear crisis last year warned that tens of millions of people, including residents of Tokyo, might be forced to leave their homes, according to a report. Fearing widespread panic, officials kept the report secret.

The emergence of the 15-page internal document might add to complaints that the government withheld too much information about the meltdown at the Fukushima Daiichi nuclear plant, the world’s worst nuclear accident since the Chernobyl disaster in 1986.

It also casts doubt about whether the government was sufficiently prepared to handle what could have been an evacuation on an extraordinary scale.

The report was submitted to Naoto Kan, the prime minister at the time, and his top advisers on March 25, two weeks after an earthquake and tsunami devastated the Fukushima Daiichi nuclear power plant, causing three reactors to melt down and generating hydrogen explosions that blew away protective structures.