Senior Tepco executive Kazuhiko Yamashita's comments on the massive radioactive water buildup at the Fukushima No. 1 plant came during a meeting with opposition lawmakers, Kyodo News reported.
Yamashita's remarks contradict Japanese Prime Minister Shinzo Abe's statement on Sept. 7 that contaminated water leaks at the plant, which was damaged during the massive earthquake and tsunami that struck Japan in 2011, were "under control."
Abe was speaking in front of the International Olympic Committee, pushing Tokyo's bid to host the 2020 Summer Olympics.
On Thursday, Tepco said radioactive substances may have also leaked into the Pacific Ocean, Kyodo said.
About 220 becquerels of radioactive substances per liter of water were found in samples taken Wednesday from a drainage ditch located near the ocean.
The Democratic Party of Japan criticized Abe for his claim that contamination at the plant was under control.
"The prime minister must back up his claim that the [radioactive water] problem is under control," DPJ Secretary-General Akihiro Ohata said Thursday. "The government has a responsibility to explain this statement to the people of Fukushima prefecture and indeed the entire country."