Camila Cabello leaves Fifth Harmony

Fifth Harmony has announced that singer Camila Cabello has left the group.

In a message posted on social media and signed by "Ally, Normani, Dinah and Lauren," the group writes, "After four and a half years of being together, we have been informed via her representatives that Camila has decided to leave Fifth Harmony. We wish her well."

The remaining members, Ally Brooke, Normani Kordei, Dinah Jane Hansen and Lauren Jauregui, state that they will continue the group as a foursome.

As recently as December 9, when the iHeartRadio Jingle Ball tour hit New York City, the group had announced plans to release a new album. Kordei told radio personality Elvis Duran, "2017, it's going to be popping" and Jane Hansen added, "The third album is definitely going to be so lit. We're really excited."

See photos of Fifth Harmony through the years:

After forming on the second season of the American version of The X Factor in 2012, Fifth Harmony released two albums beginning with Reflection in January 2015. That album included "Worth It," their first Top 20 hit on the Billboard Hot 100 chart last summer; the quintet would surpass that milestone with "Work From Home" feat. Ty Dolla $ign, the lead single to sophomore LP 7/27, which peaked at No. 4 on the Hot 100.

While the 7/27 tour brought 5H on their first international trek this year, Cabello had hinted at pursuing solo material through two successful collaborations. "I Know What You Did Last Summer," a duet with Shawn Mendes, became a Top 20 hit upon its release in late 2015. "Bad Things," a Machine Gun Kelly single featuring Cabello, has done even better, reaching No. 10 on the Hot 100 as of last week.

Although other members had expressed interest in solo careers -- Jauregui released a collaboration with pop duo Marian Hill earlier this month -- Fifth Harmony had long assured fans that a breakup or member departure was not imminent.

But insiders suggest that tensions between Cabello and the other group members had long been festering. In fact, December 18, the day the split was announced, marked the conclusion of Cabello's contractual obligations to the group and offered an exit, says a source.

Billboard has reached out to Cabello's representative for comment.