The operator of the crippled Fukushima Daiichi nuclear plant said it is studying whether the facility's reactors were damaged in the March 11 earthquake even before the massive tsunami that followed cut off power and sent the reactors into crisis. Kyodo news agency quoted an unnamed source at the utility on Sunday as saying that the No. 1 reactor might have suffered structural damage in the earthquake that caused a release of radiation separate from the tsunami. Tepco has provided a new analysis of the early hours of the Fukushima crisis. The utility said on Sunday that a review of data from March 11 suggested that the fuel rods in the No. 1 reactor were completely exposed to the air and rapidly heating five hours after the quake. By the next morning - just 16 hours later - the uranium fuel rods in the first reactor had melted down and dropped to the bottom of the pressure vessel. The No. 2 and No. 3 reactors are expected to have gone through a similar process and like No. 1 are leaking most of the water being pumped in a bid to keep their cores cool. A massive pond of radioactive water has collected in the basement of the No. 1 reactor. Experts fear that the contaminated water leaking from the plant could threaten groundwater and the Pacific.