LOS ANGELES (CBS) — Kings of Leon is canceling its U.S. tour after lead singer Caleb Followill abruptly ended a concert in Dallas over the weekend, TMZ reports.

“We are so sorry to say Kings of Leon are canceling their entire US tour due to Caleb Followill suffering from vocal issues and exhaustion,” a representative for the band said in a statement.

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The canceled dates include a show at the Verizon Wireless Amphitheater in Irvine on Sept. 8, 2011.

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However, tweets from Followill’s brother, bass player Jared Followill, hinted at trouble among band members.

“Dallas, I cannot begin to tell you how sorry I am. There are internal sicknesses & problems that have needed to be addressed. No words,” he wrote, adding in another message, “I love our fans so much. I know you guys aren’t stupid. I can’t lie. There are problems in our band bigger than not drinking enough Gatorade.”

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The band will resume touring in Canada on Sept. 28, according to TMZ.