A top U.S. Nuclear Regulatory Commission official today said the nuclear crisis in Japan is "on the verge of stabilizing," even as Japanese workers were forced to suspend relief efforts temporarily after gray smoke billowed from two reactors.
"The fact that offsite power is close to being available for use by plant equipment is the first optimistic sign that things could be turning around," said Bill Borchardt, executive director of the Nuclear Regulatory Commission Operations.
Japanese workers made significant progress over the weekend at the Fukushima Daiichi power plant connecting crippled reactor cooling systems to power lines, with the systems expected to be brought online in Units 1 and 2 today, and Units 3 and 4 in the next few days, Tokyo Electric Power Company (TEPCO) officials said.
Units 5 and 6 have already been successfully connected to diesel generators.
Restoring power to the water pumps means workers will be able to cool the cores and prevent a meltdown.
Borchardt said that while U.S. officials believe several reactors have experienced some sort of core damage, the containment structure around the radioactive core is largely intact and water is flowing to cool the radioactive rods.
"The radiation releases and dose rates that we see on site are mostly influenced by units 3 and 4 spent fuel pool," said Borchardt. "And TEPCO and the Government of Japan have been making a concerted effort to address those issues."
The effort, which has progressed sporadically over the past week, stalled temporarily today at Unit 3, which lost its roof in an explosion last week, after smoke from an unknown source began rising from it.
"Cables might have caught fire," Tokyo University professor Nato Sekimura said. "It's understandable that people evacuated to study what happened in the area to secure their safety."
Meanwhile, traces of radiation from the damaged nuclear plant were still detected miles from the plant, including in some vegetables and water supplies, raising alarm by Japanese residents and spurring U.S. officials to continue urging precautionary steps.
The State Department distributed potassium iodide tables to U.S. government personnel and their families in Japan "out of an abundance of caution" but instructed them not to consume the pills yet. Potassium iodide helps the body block absorption of some radioactive materials.
The Pentagon also ordered the aircraft carrier USS George Washington and destroyer USS Lassen to move farther out to sea off the coast of Japan out of radiation concerns.
ABC News' Luis Martinez and Kirit Radia contributed to this report.