A 21-year-old nursing home assistant from Rotterdam is under investigation for murdering one patient and attempting to kill two others, the public prosecution department said on Monday.

The male suspect is thought to have killed a female patient at a nursing home in the district of Binnenmaas, south of the port city, the department said.

The investigation began earlier this month after a woman at the nursing home became unexpectedly unwell. She was taken to hospital, where medical staff said they suspected she had been given an dose of insulin. Nursing home officials then called in the police.

Investigators also found two other suspicious incidents involving the suspect. In one case, at the same nursing home in Binnenmaas, a nursing home resident died. In the other case, in Rotterdam, a female patient also became unwell.

The man worked at a number of care institutions in the region, the department said in a statement.

The investigation is still ongoing and the man was remanded in custody on Monday.