Radiation levels spike at Fukushima nuclear plant

• Radiation around the site is at 1%2C800 millisieverts per hour
• Fourth major leak from storage tanks at Fukushima since 2011
• Radiation levels are 18 times higher than previously thought

Radiation levels in a leak at Japan's crippled Fukushima nuclear plant are 18 times higher than previously thought, the plant's operators reported Sunday.

Radiation around the site is at 1,800 millisieverts per hour — strong enough to kill a person within four hours of exposure, the BBC reports. In addition, the Tokyo Electric Power Co. (TEPCO) says it has discovered a leak on another pipe emitting radiation levels of 230 millisieverts an hour.

The incident is believed to be the fourth major leak from storage tanks at Fukushima since 2011 and the worst so far in terms of volume, according to the BBC.

TEPCO had originally said the radiation emitted by the leaking water was around 100 millisieverts an hour. However, the company said the equipment used to make that recording could read only measurements of up to 100 millisieverts.

TEPCO said it is confident it can provide safety for workers dealing with the problem, CNN reported.

"We will find out the cause of this issue and make proper countermeasures immediately, and continue to make every effort to secure safety of workers," the company said in a statement released Sunday.