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Pop singer Demi Lovato is in a Los Angeles hospital after a suspected drug overdose, US media report.
The Los Angeles Police Department reportedly responded on Tuesday to a medical emergency in the Hollywood Hills, where Lovato lives.
TMZ, which broke the story, reports she was treated at the scene with Naloxone, an anti-overdose medication, after possibly taking heroin.
The 25-year-old singer was in a stable condition, US media report.
Lovato has struggled with substance abuse for years, and appeared to relapse in recent weeks.
Last month she cancelled her show at London's O2 arena, announcing the news on Twitter hours before the concert was due to begin.
In a single released last month, Sober, she sings: "Mommy, I'm so sorry I'm not sober anymore. And daddy please forgive me for the drinks spilled on the floor."
The song ends with the lines: "I'm sorry that I'm here again, I promise I'll get help/It wasn't my intention, I'm sorry to myself."
The track release followed Lovato marking six years of sobriety in March this year.
She was due to complete the North American leg of her Tell Me You Love Me world tour with a concert in Atlantic City, New Jersey, on Thursday.
Her fans say the singer's battles with bipolar disorder, bulimia and addiction - often documented in her music - have helped them with their own struggles.
The BBC contacted Lovato's representatives on Tuesday, but did not receive an immediate reply.
As reports of her condition spread, there was an outpouring of support on social media from other celebrities and musicians.
Within hours of the report, tens of thousands of people had tweeted the hashtag #PrayforDemi.
According to US health officials, 115 Americans die from an opioid overdose every day with more than 250,000 Americans dying over the past decade.
Rise to fame
Lovato first entered the spotlight on the children's TV series Barney & Friends, and gained popularity on the Disney Channel, appearing alongside the Jonas Brothers in the 2008 Disney Channel Original Movie Camp Rock.
She released her first studio album, Don't Forget, in 2008.
In a YouTube documentary called Simply Complicated, released last October, Lovato revealed that her drug use began when she first tried cocaine at the age of 17.
"I felt out of control the first time I did it. My dad was an addict and an alcoholic. Guess I always searched for what he found in drugs and alcohol because it fulfilled him and he chose that over a family."
Lovato went to rehab for the first time in 2010. "I wasn't ready to get sober," she said in the documentary. "I was sneaking it on planes, sneaking it in bathrooms, sneaking it throughout the night".