The operator of the crippled Fukushima Daiichi nuclear power plant, Tokyo Electric Power Company (TEPCO), on Monday admitted that radioactive groundwater had leaked out to Pacific Ocean, fueling fears of contamination.

Earlier this month TEPCO said groundwater samples taken at the Fukushima showed levels of possibly cancer-causing caesium-134 had shot up more than 110 times in a few days, Australia’s ABC reported.

In July, Russia Today reported, Japan’s nuclear watchdog — the Nuclear Regulation Authority (NRA) — stated that it “strongly suspected” contamination of ground waters and possibly the Pacific Ocean.

TEPCO did not know the exact reasons for the increased readings, but initially said the radioactive groundwater was likely contained by concrete foundations and steel sheets.

“But now,” TEPCO spokesman Masayuki Ono told a news conference, “we believe that contaminated water has flown out to the sea.”

However, Ono insisted that the impact on the ocean would be limited:

“Seawater data have shown no abnormal rise in the levels of radioactivity.”

The March 2011 earthquake and tsunami off Japan’s coast knocked out cooling systems at the Fukushima plant, triggering fuel meltdowns and causing radiation leakage, food contamination and mass evacuations.

Radioactive substances have since made their way into underground water, which usually flows out to sea.

This article originally was published at Global Post.