April 2 (Reuters) - Lexi Thompson was hit with a four-stroke penalty with six holes left while leading the LPGA ANA Inspiration on Sunday, but fought back to force a playoff with South Korea's Ryu So-yeon.
Thompson had been leading by three when she was informed of the penalty, which had been incurred after a television viewer alerted the LPGA that the American golfer had marked her ball then replaced it in the wrong place on the 17th hole a day earlier.
"On Sunday afternoon, the LPGA received an email from a television viewer that Lexi Thompson did not properly replace her ball prior to putting out on the 17th hole during Saturday's third round of the ANA Inspiration," the LPGA said in a statement.
It added that after a full review it informed the player of the four-stroke penalty as she walked to the 13th hole.
Thompson gathered her composure and had an eagle putt to win on the last, but settled for birdie to force the playoff against Ryu.
Her playing partner, Suzann Pettersen, said: "I thought it was serious when two rules officials came out.
"For her to come back with those birdies shows the character she is. I have got goose bumps."
Writing by Peter Rutherford; Editing by Greg Stutchbury