Overwork had caused the death of a 31-year-old NHK female reporter in 2013, according to the labor standards inspectors, the public broadcaster said Wednesday, providing further evidence of the extreme working conditions many Japanese employees endure.

Miwa Sado, who belonged to the broadcaster's center in Tokyo and died of congestive heart failure in July 2013, worked 159 hours of overtime with only two days off in the one-month period prior to her death, a local labor standards office concluded in May 2014.

Prime Minister Shinzo Abe's administration has been seeking to improve working conditions in the country following the suicide of a new recruit at advertising giant Dentsu Inc. in 2015 due to excessive working hours.