TOKYO, Oct. 17 (Xinhua) -- Radioactive emissions from the crippled Fukushima No. 1 nuclear plant have been cut in half, the owner and operator of the plant said Monday.

According to Tokyo Electric Power Company (TEPCO)\'s latest monthly review of stabilization progress, temperatures at the plant\'s three damaged reactors have all fallen below 100 degrees Celsius -- a prerequisite for bringing the reactors to a state known as "cold shutdown" -- and have stopped emitting radioactive steam into the environment.

In a regular press conference jointly held with government officials, the utility, also known as TEPCO, said that while multiple water sources, including the availability of fresh water being pumped from fire trucks, had helped significantly in reducing the risk of further, devastating damage being caused to the plant\'s reactors, risks do remain.

TEPCO maintained that the biggest risk posed to the faltering reactors was the potential for another large tsunami to knock out key water supplies. In this worst-case-scenario vital cooling processes could be severely compromised and the temperature inside the reactors could once again rise, leading to radioactive steam leaking and the possibility of further explosions, the utility said.

The operator of the plant, central to the world\'s worst nuclear disaster in 25 years, added that another major earthquake could cause a devastating power outage at the No. 1 facility, which would have untold affects on cooling, monitoring and decontamination systems.

"Without well-trained staff on standby to deal with such problems, there is a risk of failing to restore power supply and causing damage to reactor cores," the company said at a joint news conference.

The No. 1 plant in Fukushima again came under the spotlight on Thursday as a possible reason for radiation levels spiking at two hotspots in Tokyo and Chiba prefectures, located some 200 km south of the crippled facility.

An area along a sidewalk in Tokyo\'s Setagaya Ward, frequently used by elementary school children, was found to have airborne radiation measuring 3.35 microsieverts per hour and a children\'s amusement park tested positive with 5.82 microsieverts in the Funabashi district of neighboring Chiba prefecture, local authorities said.

By way of comparison, readings taken from inside the evacuation zone in Fukushima prefecture at the same time measured 2.17 microsieverts per hour, according to local prefectural officials.

While tens of thousands of people still remain evacuated from a 20 km no-go zone around the Fukushima nuclear plant, Japan\'s nuclear safety agencies and government authorities have ramped up the monitoring of radiation levels around the country, in light of the recent spate of nuclear-related scares.