The deaths of two patients whose ventilator machines stopped working prompted investigators to search a health care provider's Brooklyn Park offices.

Police entered the headquarters of Plateau Healthcare on Friday and seized various medical records, correspondence and other potential evidence in the deaths of Douglas E. Palm, 49, on Sept. 10, 2016, and Taurus L. Grantham, 41, on Oct. 18, 2017.

Police opened a criminal investigation in the wake of Grantham's death. Palm's death came to light after a relative saw news reports about Grantham and contacted authorities.

Both men were stricken with amyotrophic lateral sclerosis (ALS) a chronic neuromuscular disease known as Lou Gehrig's disease, according to the search warrant affidavit. In both cases, Plateau nursing staff allegedly failed to respond when the men's ventilators stopped.

Faisale Boukari, president of Plateau Healthcare, a home care agency with about 100 employees in the Twin Cities area, said Monday that his company is cooperating with police in their investigation.

The search also included the employment file of the nurse police say was Grantham's sole care provider at the time he died. Police have not arrested the 45-year-old nurse, nor has she been charged. The Star Tribune generally does not identify suspects before they are charged.

Boukari told the Star Tribune that Palm's nurse was not the same as Grantham's. Police said they are still working to identify Palm's nurse.

The additional fatality came to light after news coverage of Grantham's death prompted Palm's sister to contact police on June 14, the search warrant affidavit showed. Police conducted their search eight days later and are also seeking hospital and ambulance records for both men, according to recently filed search warrant affidavits.

Gloria Dahlke said her brother had been at Plateau's facility on June Avenue in Brooklyn Center for about three weeks when he "had stopped breathing," the court filing read.

A woman from the facility called Dahlke and said "the alarm on some medical equipment had gone off, however, it went unnoticed," the filing continued. Palm, a father of two from Maplewood, died soon afterward.

Dahlke said on Monday that the nurse "on the phone said that she had been out smoking and did not hear his alarm. He had been without oxygen for about 20 minutes."

In Grantham's case, the state's investigation determined the nurse tried to cover up her failure to detect that his ventilator machine was not plugged in and had a critically low battery, triggering multiple alarms. The St. Paul man was found dead about 6:25 the next morning, more than seven hours after he was last checked.

The nurse associated with Grantham's death no longer works for Plateau but continues to hold a state nursing license as of Monday, according to the Minnesota Nursing Board.

Shirley Brekken, the board's executive director, said Monday that her agency has taken no disciplinary action against the nurse "at this time," adding that she is prevented by law from publicizing whether any complaints against her are pending.

"If this lady is negligent [in either or both deaths] and still working, we don't want that to happen," Douglas Palm's wife, Debbie, said.

Debbie Palm said she's unaware of any state Health Department review of her husband's death, and a spokesman with the department office that investigated Grantham's death said there has been no similar inquiry into what led to Palm's death.