TOKYO -- Experts who investigated Japan's nuclear crisis say a watchdog's oversight of the crippled plant's operator is still too lax.

The Fukushima Dai-ichi plant has been plagued with glitches. A blackout last month left the plant's fuel storage pools without cooling for more than a day. Last Friday another cooling failure occurred, and hours later the operator reported a massive contaminated water leak from underground tanks.

The investigators said Monday that the Nuclear Regulation Authority is only rubber-stamping work by operator Tokyo Electric Power Co. at the plant that runs on makeshift equipment.

Nine of the 10 members testified at a lower house nuclear committee for the first time since releasing their findings in July. The report called the March 2011 disaster "manmade," and blamed regulator-operator collusion and botched crisis management.