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.

As a reporter in charge of covering the Tokyo Metropolitan Government, Sado worked on the Tokyo Metropolitan Assembly election and the House of Councilors election from June to July 2013. She died on July 24, three days after the Upper House election.

NHK said it kept track of her working hours through personal statements and time cards but acknowledged there were areas requiring improvement.

Sado joined the broadcaster in 2005 and started to work at its bureau in Kagoshima Prefecture. She was transferred to Tokyo in July 2010 and was in charge of covering the Tokyo Metropolitan Government for two years.

Masahiko Yamauchi, senior official at NHK’s News Department, said the incident was not a personal matter but a “problem for our organization as a whole, including the labor system and how elections are covered.”

On why it had taken more than three years to make the case public, Yamauchi said the broadcaster took into account the wishes of her family. Sado’s family said they wanted to ensure such an incident never happens again.

“Even today, four years after, we cannot accept our daughter’s death as a reality,” Sado’s parents said in a comment released by NHK. “We hope that the sorrow of the bereaved family will never be wasted.”

The suicide of 24-year-old Dentsu employee Matsuri Takahashi in April 2015 caught national attention, and the conclusion by labor standards inspectors in September 2016 that it was caused by sparked debate on the harsh working conditions in the country.

Dentsu is also on trial for labor practice violations, with a ruling set to be handed down on Oct. 6 by a Tokyo court.