Private sector hiring unexpectedly contracted in June, payrolls processing firm ADP said Wednesday, in a possible sign that the economy may not be as sturdy as investors believe as they bid the S&P 50

U.S. private payrolls fell for the first time in more than two years in June as economic uncertainty hampered hiring, but low layoffs continued to anchor the labor market.

The ADP employment report revealed that 33,000 nonfarm private jobs were unexpectedly lost in June, down from the 29,000 addition in May.