Niall Horan suddenly disappeared from the stage upon singing the song "18" during One Direction's Apply Music Festival performance on Tuesday.

Other members of the Brit group felt a little worried and had a bit of panic. "Where's the Irish one?" Louis Tomlinson joked. "We've lost another one! We're dropping like flies!" Harry Styles commented.

Then, Liam Payne said he think Niall was ill. "Niall has just developed a sudden sickness," he said.

Reports that Niall left the gig in an ambulance after nearly passing out spread like wildfire. Aside from the boys, several fans of the singer were also alarmed after learning the news.

However, the 22-year-old hunky singer explained the heat was getting to him at that time which caused him to feel ill so he decided to exit.

"There was no ambulance don't worry.. I just overheated on stage and didn't feel well https://t.co/ORfzQqpnmU," Niall wrote in a post on his official Twitter account.

To recall, the event became a trending topic worldwide when Little Mix served as the opening act for the popular all-male group. Several reports claimed that the concert between the two Brit groups was a "major diss" aimed at Zayn Malik - given that he departed the group in March and broke up with Perrie Edwards last month.

Zayn decided to end his relationship with Perrie after leaving the group. "Zayn and Perrie had been struggling for months. She's been touring and he's been focusing on the second chapter in his career," a source told HollywoodLife. "They barely saw each other and they hadn't even had sex in over two months." It was also divulged that the two were not on good terms after the split.

"We have a hard time believing there was no tension between [Malik] and the boys," the publication said despite the singer and his previous bandmates having recurrently guaranteed fans that they're on good terms. "We are sure that Zayn wasn't thrilled to see his ex-girlfriend opening for his ex-band," the media outlet claimed.