Bieber and Gomez ended their two-year-old relationship because of trust issues between them, US Weekly reported.
"Selena broke up with Justin about a week ago. It's been a really challenging experience over the last year because of their crazy schedules," a source told US Weekly. "Selena definitely had some major trust issues with Justin."
According to the source, the breakup, which happened during Halloween, might be temporary.
"They are [young] . . . it changes from day to day. Right now it is a break and tomorrow it could be back on knowing them . . . it's hard to say how they will end up. Maybe she feels more serious about it this time. We'll see," the source told the weekly.
After months of speculation the couple went public with their relationship in February 2011 when they appeared together at a Vanity Fair Oscar party.