A 63-year-old man and a 58-year-old woman from Zwaag, near Rotterdam, have been arrested in connection with a cold case investigation into the death of the woman’s daughter in 2012.

The two are suspected of involvement in the death, which was first classed as a suicide, the public prosecution department in Rotterdam said.

What the department calls ‘new insights’ have now led investigators to conclude that the couple may have murdered the young woman, by giving her a ‘deadly substance’.

The cold case team began investigating the death after the female suspect’s other daughter killed herself in 2016. That is said to have happened after the young woman, aged 26 at the time, had been sexually abused in a psychiatric care institution. The owner of the institution is under investigation for that crime and will appear in court on February 20.

However, the 58-year-old woman, also worked at the institution, the public prosecution department said. And according to RTL Nieuws, the couple are suspected of involvement in three other murders at the institution, including that of the woman’s other daughter.

RTL said the clinic involved is a Christian therapeutic care institution called Hoeve Jedidja which was at the centre of a sexual abuse storm in 2014.

The couple have been remanded in custody for a further 30 days while the investigation continues.