Justin Gaston and Miley Cyrus
DiCapua/Splash News Online
06/09/2009 AT 03:45 PM EDT
In recent days, Miley Cyrus
and Justin Gaston have taken to their separate Twitter pages with messages of woe.
"Tears are words the heart can't express," Cyrus, 16, wrote Sunday night. Gaston, 20, tweeted the next morning, "How many tears are in there? They've gotta run out soon, right?"
On Tuesday, a source confirms the reason behind the tears. "They broke up on Sunday before she left for Savannah" to film her new movie, The Last Song
, the source tells PEOPLE.
The pair was last spotted together on Friday at the Hannah Montana
wrap party in Los Angeles. "Miley introduced him to people," an insider says. "There was no hint [of problems]. They were a couple as usual."
Two days later came the Twitter posts. No official reason has been given for the breakup, first reported on E! Online
. But Cyrus has recently been spending a lot of time with ex Nick Jonas – with whom she sang the duet "Before the Storm," which premieres Friday on Radio Disney.
"They have been recording music and spending more time together," says the source. Cyrus and Jonas, 16, also saw each other in L.A. on Saturday for Disney's Friends for Change video shoot.
Reps for Cyrus and Gaston had no comment.