Deputies responded shortly after 7:30 p.m. to the 23800 block of Elyce Court, where one man was pronounced dead at the scene, according to the Riverside County Sheriff's Department. His identity was not immediately released.
Three other men were transported to a hospital "for treatment of life-threatening injuries," a sheriff's news release said Sunday morning. "Early findings would indicate drugs are a factor in the death and we do not suspect foul play."
News video from the scene showed paramedics loading patients into ambulances at the end of a cul-de-sac lined by single-story homes.
The substance involved was unknown, authorities said in a previous statement.
The sheriff's Overdose Death Investigations and Narcotics Unit assumed the investigation.
Anyone with information about the incident is urged to call sheriff's Master Investigator Cornett at (951) 955-1700.