The singers have dated off and on since 2010, and were widely believed to have broken up for good late last year.
UsMagazine.com said the current status of their romance is unclear despite Gomez' appearance at Bieber's concert Thursday night.
"They have a crazy connection," a source told the magazine. "They just can't seem to break their connection. It can be intense."
2014: The Year in Music [PHOTOS]