Princess Aiko, the only child of Crown Prince Naruhito and Crown Princess Masako, has been absent from junior high school for a month due to poor health, an Imperial Household Agency official said.

The 14-year-old princess has missed school since Sept. 26 because of fatigue from examinations after the summer vacation and preparation for a school athletic meet, the official said Tuesday.

The Crown Princess took her to the Hospital of the Imperial Household on Oct. 6, where no particular health problem was found, according to the official.

The princess "does not have to keep to her bed all day long. She took a walk in a garden for a little while yesterday," said Nobutake Odano, grand master of the Crown Prince's household.

He said, however, no schedule has been set for her return to school.

"According to her doctor, although her condition has been improving little by little, it may take some more time for recovery," Odano said.

The princess spent a busy summer vacation, traveling with her parents who attended a ceremony in Tokyo on Aug. 1 and a Mountain Day event in Matsumoto, Nagano Prefecture, on Aug. 11.

The Crown Princess canceled a plan to travel with the Crown Prince last Friday to Sunday for a ceremony in Iwate Prefecture due in part to being tired from taking care of her daughter.

Princess Aiko, who is now in her third year at Gakushuin Girls Junior High School in Tokyo, was occasionally absent when she was in her second to fourth years in elementary school.