Robots collected the data, which shows a harsh environment. Officials said the buildings are still too radioactive for repair crews to enter.
Workers have not been able to enter the reactor buildings at the stricken plant since the first days after the cooling systems were wrecked by the March 11 earthquake and tsunami that left more than 27,000 people dead or missing.
Officials hope to have the plant under control in six to nine months. It remains unclear when people living nearby will be able to return home.
The area needs to be decontaminated and police are still searching for people killed in the disasters.
Officials said Monday that radiation had spiked in a water tank in Unit 2 and contaminated water was discovered in other areas of the plant, underscoring the growing list of challenges facing Tokyo Electric Power Co. in cleaning up and containing the radiation.
They also described in more detail the damage to fuel in three troubled reactors, saying pellets had melted.
The Associated Press contributed to this report.
