FUKUSHIMA, Japan (AP) — Emergency workers forced to retreat from a tsunami-stricken Japanese nuclear power plant when radiation levels soared prepared to return Wednesday night after emissions dropped to safer levels.The pullback cost precious time in the fight to prevent a nuclear meltdown, further escalating a crisis spawned by last week’s devastating earthquake and tsunami that pulverized Japan’s northeastern coast and likely killed more than 10,000 people.It was unclear what happened in the Fukushima Dai-ichi nuclear plant’s overheating reactors after late morning, when the workers stopped pumping in seawater trying to cool their fuel rods. Officials gave only sparse information about the reactors.But conditions at the plant appeared to be worsening. White steam-like clouds drifted up from one reactor which, the government said, likely emitted the burst of radiation that led to the workers’ withdrawal. The plant’s operator reported a fire at another reactor for the second time in two days.At one point, national broadcaster NHK showed military helicopters lifting off to survey radiation levels above the complex, preparing to dump water onto the most troubled reactors in a desperate effort to cool them down. The defense ministry later said it said it had decided against making an airborne drop because of the high radiation levels.