BROOKLYN PARK— Police have seized records from a Minnesota home care agency as they investigate the deaths of two patients whose ventilator machines stopped working.

Brooklyn Park investigators collected potential evidence from Plateau Healthcare following the deaths of Douglas Palm, 49, in September 2016 and Taurus Grantham, 41, in October 2017. Both men had Lou Gehrig’s disease, or ALS.

A search warrant affidavit says in both cases Plateau nursing staff failed to respond when the ventilators stopped working.

Palm’s sister, Gloria Dahlke, said her brother “had been without oxygen for about 20 minutes.” The state’s investigation has also determined that Grantham was pronounced dead more than seven hours after he was last checked.

The police search included the employment file of a nurse who was caring for Grantham before his death, The Star Tribune reported. The nurse no longer works for the agency but had a state nursing license as of Monday, according to the Minnesota Nursing Board.

Shirley Brekken, the board’s executive director, said that her agency hasn’t taken disciplinary action against the nurse “at this time,” adding that she’s prevented by law from publicizing whether any complaints against her are pending.

Police said they’re still working to identify Palm’s nurse.