LEWISTON — A 31-year-old transient was rushed to a local hospital Friday morning after overdosing on heroin, police said.

Emergency crews answered a 911 call from 63 Howe St. where the woman was found unconscious. She had arrived at that address reporting she had taken drugs, was feeling funny and had to lie down, Lt. Michael McGonagle said.

The apartment’s tenant realized she had overdosed and called for help at 8:15 a.m., he said.

The ambulance crew administered the drug Narcan, also known as naloxone, used to counter the effects of an opioid overdose. A Maine law allowing first responders to administer the drug was enacted in April after legislative approval.

The woman regained consciousness and is expected to recover fully, officials said.

Police said this was the second time the woman had overdosed on heroin.

Detectives are seeking to determine where the heroin came from and whether it is linked to a spate of heroin overdoses earlier in the week.

According to one medical official, some of the heroin circulating locally is mixed with fentanyl, a pain reliever that also acts as a muscle relaxant. The fentanyl produces an intensified high that users may not be prepared for. Around the country, the mix has been blamed for more than 100 deaths since late last year.

Earlier in the week, four people suffered heroin overdoses in downtown Lewiston, police said. All four victims survived. Police and drug agents were working to identify the source of the drug.