LOS ANGELES (CBSDFW.COM/CNN) – Demi Lovato is experiencing “complications” and remains hospitalized following her apparent drug overdose, two sources close to the singer told CNN. Those complications include “nausea, vomiting and a high fever,” the sources said.

Lovato is expected to “make a full recovery,” but there is “no estimate” as to when she will be released from Cedars-Sinai Medical Center in Los Angeles. “Taking it day by day,” one of the sources said.

No information has been released regarding what led to her hospitalization. There had been reports that Lovato overdosed on heroin, but a source close to the singer denied that information.

Last week, a source with knowledge of the matter told CNN that Lovato plans to seek drug abuse treatment following her release from hospital care.

CNN previously reported that Lovato’s family and her former boyfriend, “NCIS” star Wilmer Valderrama, have been by her side since her hospitalization one week ago.

At the time of her apparent overdose, a representative for Lovato released a statement. “Demi is awake and with her family, who want to express thanks to everyone for the love, prayers and support,” the statement read. “Some of the information being reported is incorrect and they respectfully ask for privacy and not speculation as her health and recovery is the most important thing right now.”

Demi Lovato

(credit: Kevin Mazur/Getty Images for Philymack)

Lovato has been very open about her struggles with cocaine and alcohol addiction, as well as her mental health issues and an eating disorder. She also sought professional help for substance abuse and entered rehab in 2010.

“You just have to take it one day at a time. Some days are easier than others and some days you forget about drinking and using. But for me, I work on my physical health, which is important, but my mental health as well,” Lovato explained, adding that she was seeing a therapist twice a week. “I make sure I stay on my medications. I go to AA meetings. I do what I can physically in the gym. I make it a priority.”

In the hours after the news of her hospitalization broke, the singer’s fans took to social media to talk about how Lovato and her music have helped them with their own struggles. They used the hashtag #HowDemiHasHelpedMe.

The hashtag #PrayForDemi also trended on Twitter as celebrities posted supportive words — including Missy Elliott, Ariana Grande, Brad Paisley, Kesha, Bebe Rexha, Meghan Trainor, Maren Morris, Kehlani and British electronic group Clean Bandit, whose current single “Solo” features Lovato.

Lovato released a single in June called “Sober,” in which she revealed that she had relapsed after six years of sobriety. “I’m sorry for the fans I lost who watched me fall again,” Lovato sings. “I want to be a role model, but I’m only human. I’m sorry that I’m here again. I promise I’ll get help.”

Lovato had been touring and promoting her music in recent months. Her last performance was on July 22 in Paso Robles, California.

Lovato grew up in North Texas and her mother is a former Dallas Cowboys Cheerleader from Irving.

After appearing as a child actress on television’s “Barney & Friends,” Lovato broke onto the scene as a teen on the Disney Channel film “Camp Rock” and the network series “Sonny with a Chance.” She then became a multi-platinum pop star with hits like “Sorry Not Sorry” and ”Confident.”

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. Cable News Network, Inc., a Time Warner Company contributed to this report.)