A 59-year-old man has died and three others were sickened by carbon monoxide poisoning inside a Bernardsville home, according to the police department.

Police say that first responders were called to 92 Chestnut St. just after 5:30 a.m. Thursday for reports of an unconscious man in need of medical attention. Police officers began performing CPR but the man was pronounced dead at the scene.

First responders reported a strong smell of gaseous fumes coming from the home. They took three other people living in the home to the hospital for treatment. The names of those affected were not released, but the three taken to the hospital were identified as a 51-year old woman and two children ages 17 and 9. All three have since been released from the hospital.

Police have not officially released the cause of the carbon monoxide leak.

The Somerset County Prosecutor’s Office is investigating the incident.