Over a week after a man died and four others were hospitalized in a odor incident in Denver, investigators are still determining the mysterious cause.

The Denver Office of the Medical Examiner identified the victim as 33-year-old Daniel Antoine on Thursday following the death that occurred Nov. 12. Still, no cause of death has been determined as investigations continue, according to the office.

The incident occurred at a home in the 19000 block of East 41st Place — in the Green Valley Ranch neighborhood — around 8 a.m. The Denver Fire Department initially responded to the home after a resident claimed to have had trouble breathing, according to the department. Upon arrival, fire crews and Denver Health assisted several people.

Antoine was pronounced deceased around 10 a.m. and four — two adults and two children — were taken to a nearby hospital, according to the fire department. Two other people were assisted and not taken to a hospital.

The Denver Police Department then took over the investigation, eventually determining that the death was not criminal in nature. On Thursday, the police told The Denver Gazette that the incident still does not appear to be criminal, but offered no other information.

Following the death, the close-knit neighborhood began thinking of the possibility of a carbon monoxide leak, causing residents to take a look at their own detectors.

“It’s unfortunate and sad, but it can happen to all of us,” Tammy Fitch, a neighbor who has lived in the area for 20 years, said, calling the situation a wake-up call.

“Thank goodness I just installed a carbon monoxide detector,” she said. “It doesn’t scare me, but it’s sad. It made think, like, should I even install one downstairs?”

While carbon monoxide poisoning can happen within minutes, according to Cleveland Clinic, carbon monoxide leaks are odorless.

Furthermore, Xcel Energy — who provides utility and natural gas services to the area — told The Denver Gazette that there was no natural gas leak or odor issue after its separate investigation, noting that any additional investigations would be done by the police department.

According to neighbors, the home was rented by a family around a year ago. Whether Antoine was part of that family is still unknown.

The police department did not provide information about the status of the other people affected during the incident.

Answers on what occurred and caused the mysterious death will remain in the air until the medical examiner receives the results of its toxicology tests, which could take several weeks.