Three men were pronounced dead Thursday after being found unresponsive on a street in San Francisco's Haight-Ashbury neighborhood, according to police.
The San Francisco Department of Public Health stated that the deaths are being investigated as drug related.
"We do not have confirmation at this time of the cause of death, but we are concerned about the possibility of fentanyl poisoning," a statement from the department read.
The men were found just after 4:30 a.m. along the 1500 block of Page Street, police said. First responders tried to save the men, but they were later pronounced dead at the scene.
Police said that they do not suspect that foul play or weather played a role in the deaths.
Public health officials said that fentanyl, an extremely potent opioid that is sometimes used to cut street drugs, was responsible for 22 deaths in San Francisco in 2016. Most of those were associated with opiates or methamphetamine, but 27 percent involved cocaine.
One person died from fentanyl poisoning after ingesting counterfeit Xanax pills in Oct. 2015 and another died after ingesting crack cocaine laced with fentanyl in May 2017.
Public health officials are advising users of street drugs to carry Naloxone, more commonly known as Narcan, which can save lives if administered to opioid overdose victims if used properly.
An investigation into the deaths is underway.
Bay City News contributed o this report.