NAGOYA (Kyodo) -- The bereaved family of a Sri Lankan woman who died in detention at an immigration facility in Japan in 2021 will file a lawsuit seeking the disclosure of all security camera footage leading up to her death, the family's lawyers said Thursday.

The Japanese immigration authorities rejected a call for releasing additional footage of Ratnayake Liyanage Wishma Sandamali in a decision dated March 26, and her family plans to challenge the decision at the Tokyo District Court possibly in May.

At a press conference in Tokyo, younger sister Wayomi, 32, said through an interpreter that she wants to know why her otherwise healthy sister suddenly died, expressing dissatisfaction with the decision not to release the footage.

Wishma's 30-year-old sister Poornima, who participated online, said her bereaved family had a right to the footage.

Lawyer Shoichi Ibusuki said, "It is grossly unfair to refuse the release of the footage, which shows an official's actions in the line of duty and should not be problematic to disclose."

Wishma died in March 2021 at the age of 33 while being held at a facility of the Nagoya Regional Immigration Services Bureau. She came to Japan in 2017 as a student but was taken into custody in August 2020 for overstaying her visa.

She complained of ill health, which included vomiting and stomachaches, for around a month during detainment, and her death sparked national outrage over her treatment.

Wishma's family is separately seeking damages from the government over her death, alleging she was illegally detained and died due to a lack of necessary medical care.

A five-hour-long video clip out of 295 hours of security camera footage was submitted by the Japanese government in the damages suit and aired in court in June and July of 2023. Wishma's family has sought the rest of the footage.

Some of the released footage taken less than two weeks before her death showed Wishma lying on a bed and begging officers to take her to a hospital after telling them she could not move or eat.

The footage also included later scenes of an officer and nurse cheerfully chatting while tending to Wishma as she moaned in pain.

In an excerpt from the day she was confirmed dead, an officer tried to wake an unresponsive Wishma after reporting over an intercom that her fingertips felt cold.

The immigration authorities refused to disclose the rest of the footage, saying it may "interfere with public safety and the maintenance of order" by revealing information about the operation of security systems.