A 98-year-old woman’s death in a south suburban Chicago assisted living facility has been ruled a homicide. She and five others were hospitalized in early February after suffering breathing difficulties. The Cook County Medical Examiner’s made the announcement Monday.

Police say Dorothy Byrd died Feb. 4 from morphine and hydrocodone toxicity, combined with hypertensive and atherosclerotic cardiovascular disease. She died one day after she and five other Holland Home residents were sent to the hospital complaining of respiratory and blood pressure issues. The facility is in South Holland, IL.

Since then, two of the other hospitalized residents, Robert Rundin, 88, and Leon Krynicki, 98, also have died. Police told a local newspaper the causes of their deaths are being investigated. Authorities said it could take up to two months for tests to be conducted and analyzed to determine Krynicki’s cause of death. Rundin’s cause and manner of death are also still pending, according to a published report.

“We’re continuing to cooperate closely with local law enforcement’s ongoing investigation and are referring all questions to them until that’s concluded,” David Mills, COO of Villa Healthcare, which manages Holland Home, said in a written statement to the Daily Southtown newspaper. “Our own internal investigation is also ongoing, consistent with our commitment to provide quality resident care.”