Adam Levine and Blake Shelton appear to be the best of friends. Sure, The Voice co-stars often bicker on the show but their spats have always been in good fun... or have they?

According to a new report, Levine and Shelton's bromance may have come to an end after starring alongside one another for the past 13 seasons of the NBC singing competition.

On Oct. 30, Life & Style magazine cited a potential rift between Levine and Shelton, explaining that the alleged on-set drama between Miley Cyrus and Jennifer Hudson, who was added to the show earlier this year, had led to a feud between the guys.

"Blake and Adam's bromance has cooled off," a source told the magazine on Monday. "They definitely aren't as close as they once were."

That said, the magazine's insider states that because Levine and Shelton are known to argue back and forth during the show, their alleged feud will likely go unnoticed as the 13th season of the show continues to air on NBC.

When cameras aren't rolling, the friendship between Levine and Shelton "seems forced," the source continued. "It's not as natural as it once was. They've definitely drifted apart."

As for Cyrus and Hudson, their drama reportedly came to an end earlier this season after Cyrus allegedly put a spotlight on Hudson's long engagement to fiance David Otunga. As an insider explained to the magazine, Hudson reportedly looked Cyrus right in the eye and demanded she never mentions her private life on set.

Levine and Shelton first began starring on The Voice during its first season in 2011. Since then, they have remained as the show's stars as other judges, including Shelton's girlfriend, Gwen Stefani, have come and gone.

“I remember when I saw him at the meeting at NBC, I was instantly very taken by him ’cause he was definitely not your typical country artist,” Levine told People. “He was not a cookie-cutter guy, and the second we met, we were friends. All of the bulls*** that we do comes from a place of love.”

To see more of Adam Levine and Blake Shelton, and their co-stars, including Miley Cyrus and Jennifer Hudson, tune into new episodes of The Voice season 13 on Monday and Tuesday nights at 8 p.m. on NBC.