What caused the sudden breakup of Shania Twain and her husband, music
producer Robert "Mutt" Lange, after 14 years of marriage? His
relationship with another woman, say several sources.


Reached by PEOPLE after the separation was announced in a statement, Lange called the split "an unfortunate thing." He added, "It's literally just a growing apart, that's all."


But sources close to the situation say a third party was
involved: Marie Ann Thiébaud, a longtime secretary and manager of the
couple’s chateau in Switzerland. "Mutt and Marie Ann left their spouses
for each other and are still in a relationship," says one source.

Lange denies the claims. "It's absolutely not the reason [for
the separation]," the famously reclusive producer told PEOPLE when
asked about the alleged affair. He also denied that he was in a
romantic relationship with Thiébaud: "I'm not, no," he said. "It's not
true." (Thiébaud could not be reached for comment.)

Twain, 42, and Lange, 59, married in 1993. They have a 6-year-old son, Eja (pronounced "Asia") D'Angelo.


An insider says the "You're Still the One" singer is
"devastated. This came out of left field. . . She loved him." Another
source close to Twain tells PEOPLE the Canadian-born star is coping
with the help of "a very close-knit group of family and friends."

By Alexis Chiu