TOKYO- Substance believed to be nuclear fuel debris has been found at the bottom of a crippled reactor at the Fukushima No. 1 power plant, Tokyo Electric Power Company Holdings Inc. said Saturday.

The operator of the northeastern Japan plant, hit by the 2011 nuclear disaster, announced the results of the third round of its probe into the containment vessel of the No. 3 reactor using an aquatic robot.

The vessel holds water up to 6.4 meters from the bottom, because nuclear fuel debris, formed due to the meltdown inside the reactor, needs cooling. The robot captured underwater images by using its cameras.

The debris-like substance was among objects seen one to 2 meters from the bottom, which also included fragments of structures inside the reactor.

The No. 3 reactor is one of the three reactors that experienced meltdowns in the nuclear disaster, which followed the March 2011 earthquake and tsunami. In the No. 3 reactor, most of the nuclear fuel is believed to have melted and fallen through the pressurized vessel, which is inside the containment vessel.

The government and TEPCO plan to decide this summer how to remove the debris.

The robot entered the containment vessel on Wednesday and captured images of the lower part of the pressurized vessel on Friday, obtaining images of debris-like substance for the first time. On Saturday, the machine went deeper near the bottom of the containment vessel.

With the third round, TEPCO finished the aquatic robot probe. The company will analyze captured images further in hopes of determining whether the substance in question is fuel debris. (Jiji Press)