Japanese authorities tried pouring water on overheated reactors from a helicopter but abandoned the effort because of radiation risks.

Tokyo Electric Power Co., operator of the collection of nuclear reactors at the Fukushima Daiichi plant suffering major problems after an earthquake and tsunami, hopes a new power line will alleviate cooling difficulties.

The plant has been without power since Friday's magnitude 9.0 earthquake, and backup generators to keep the nuclear fuel from overheating failed after the tsunamis. But the power company is working to connect new power lines, according to media reports, a move that could restore cooling systems.

The power line is almost complete, Canada's Globe and Mail quoted Tokyo Electric Power Co. spokesman Naoki Tsunoda as saying. He didn't predict when it would be finished, though.

This illustration, based on a GeoEye satellite photo viewed through Google Earth, shows the locations of the six Fukushima Daiichi nuclear reactors.

High radiation levels prevented workers from connecting the lines to the power plant facilities using a "makeshift switchboard," NHK, Japan's state broadcaster, said Thursday. (NHK broadcasts over Ustream for those who want live updates from Japan.)

Wednesday's efforts at cooling reactor buildings included an aborted attempt to drop water from a helicopter. Another plan involves spraying water from a water cannon.

Fukushima Daiichi has six reactors. Numbers 1, 2, and 3 were operating when the earthquake struck, while numbers 4, 5, and 6 had been shut down for an inspection. All have cooling requirements, since even when not operating nuclear fuel can be extremely hot. Excess heat, if not removed with circulating water, can cause fuel rods to melt, leading to much greater risks of contamination.

Friday's magnitude 9.0 earthquake and its resulting tsunamis have killed thousands, with thousands more missing.

Steam rising from a nuclear reactor at the Fukushima Daiichi plant.