(CNN) -- Justin Bieber is pledging to raise the bar as new photos alleging marijuana use have hit the Web.
In pictures posted by TMZ on January 4, the 18-year-old is seen holding what the site claims is marijuana while hanging out with other young adults in what appears to be a hotel room.
Bieber's reps have not commented on the photos or allegations of marijuana use, which have circulated since a paparazzo died in a traffic accident last week after taking pictures of Bieber's parked Ferrari.
TMZ reported that the photographer said he saw Bieber driving and smoking what he believed was marijuana from a pipe hours before the accident occurred.
At the time, the teen's representation told CNN, "It's really sad that people are trying to push a story without the facts so soon after this tragic accident. Justin was not present or involved in this incident and the focus should remain on honoring the memory of the victim."
Bieber himself has not commented on the images, but he did take to Twitter not long after they were posted to tell fans he's making an effort toward improvement.
"[E]veryday growing and learning. trying to be better. u get knocked down, u get up," Bieber tweeted after midnight January 5. "[I] see all of u. i hear all of u. i never want to let any of you down. i love u. and..thank u. ... like i said...2013...new challenges. new doubters...Im ready. We are ready. see u all tomorrow and everyday after that."
Later that day, Bieber arrived in Utah for a performance and, as he has in the past, made time for a fan in need of an uplift.
According to Salt Lake City's KSTU, the singer visited a 7-year-old fan named Millie Flamm who's battling leukemia. Flamm had tickets to Bieber's concert that Saturday but couldn't attend after a relapse sent her back to the hospital.
Flamm's father told the CNN affiliate that she has been fighting leukemia for a little more than three years. KSTU reports that a group of moms urged Bieber via Facebook and Twitter to pay Flamm a visit when he came in town, but no one knew if he'd make it.
That night he did, much to Flamm's surprise - she had no idea others were petitioning for his visit on her behalf.
CNN's Denise Quan contributed to this report.