Japan’s ability to control a rapidly escalating nuclear crisis was under increased international scrutiny after radiation levels spiked dramatically at a nuclear power plant, forcing helicopter pilots to abandon their efforts to cool an overheated fuel storage tank with water.

Earlier on Wednesday Tokyo Electric Power ordered its skeleton crew of 50 remaining workers to move away temporarily from the six reactors inside the Daiichi Fukushima plant after radiation levels jumped to 10,000 times normal levels. They later fell back to a third of that level. The workers returned after about 45 minutes. A pool of 180 workers is on rotation to monitor the plant.

Plumes of white vapour were seen pouring from what authorities identified as?the?station’s?No 3 reactor. Tepco said part of the reactor’s?reinforced?containment vessel might have been damaged, but technicians were unable to determine the exact source of the vapour leak.