Justin Bieber passed out while finishing his London concert at the O2 Arena on Thursday night, according to numerous reports.
According to E! News, Bieber was seen having breathing problems towards the end of his concert in London, and he apparently ended up fainting on stage, according to some eye witnesses.
A rep. for Bieber has told E! that the Canadian pop star "got oxygen from emergency personnel. He insisted on finishing the show. He is on the way to the hospital right now."
Sources have also told E! that Bieber announced to his fans at the concert that he wasn't feeling well. After the incident he was taken backstage by medical staff for about 10 minutes, according to report, where doctors advised him not to continue with the show. However, it is said that after about a 10 minute delay Bieber insisted he go back and out and he eventually went back on stage and finished his gig.
On Wednesday night, Bieber was seen at his hotel in London wearing a gas mask - it was the second time he has been seen wearing on since he arrived in the U.K.
According to reports, Bieber was later taken to hospital where he remained on Thursday night receiving a thorough medical check up to ensure he was alright.
Rumors have been swirling this week that Bieber was having a "meltdown" after numerous bouts of erratic behavior from the teenage pop star in recent days and weeks.
Earlier this week on Tuesday motorists in East London described his behavior as "peculiar" after he was allegedly seen hopping between cars on a busy London road near the O2 Arena.
The incident allegedly took place after his concert at the arena earlier that night.
Tuesday was the second gig at the O2 for Bieber on his current tour - he arrived on stage a few minutes early, according to fans, after previously angering fans in the previous night's concert when he turned up two hours late for the start of his gig.
According to the UK's Daily Mirror, a motorist described about Bieber: "He was acting really peculiarly, car-hopping around a procession of black Bentleys, surrounded by motorbikes, all sporting Canadian flags while traffic was at a standstill. It was all a bit odd."
According to Entertainment Wise, an industry insider has suggested that the people around Bieber are now becoming increasingly worried about his erratic behavior.
An unnamed music executive allegedly has said, "There have been mutterings behind closed doors that Justin's attitude needs to be seriously addressed."
The source added: "He is one of the planet's biggest stars and has been surrounded by 'yes' men for most of his teenage life. As a result, he seems to feel he can go around unchecked without fear of the consequences. He is still a massive earner for the company but this doesn't mean he can treat people with disregard."
On Monday, hundreds of young fans were forced to leave Bieber's O2 concert before it began despite having paid to watch him perform. The singer reportedly arrived at 10.30 p.m. local time, which was just minutes before the show was scheduled to end, forcing many of his young fans to either stay up past their bedtime or leave early.
Bieber tweeted after complaints started flooding in: "I was 40 min late to stage."
Bieber, 19, was reportedly scheduled to begin the show at 8.30 p.m., but the singer is adamant that reports about him being two hours late are inaccurate. He said, "Last night i was scheduled after 3 opening acts to go on stage at 935 not 830. But because of some technical issues i got on at 10:10."
The crowd eventually began booing the Canadian singer as their frustrations boiled over.
Here is a video of the O2 crowd hearing an announcement after Bieber's collapse: