CNNMoney reported that investors finally appear secure enough about the economy to leave the safe haven of Treasuries, pushing yields on the benchmark 10-year note briefly above 2.3 percent on Thursday — the highest level since October. Yields had been hovering below 2 percent for most of the past seven months.

Bond rates rise when prices fall. Typically, investors sell bonds and move back into stocks when they become more bullish about the market’s prospects. The yield surge started after an announcement following the Federal Reserve’s Open Market Committee meeting that said the central bank is more optimistic about the health of the U.S. economy.

This week’s moves in the Treasury market are a sign that what has been considered a bond bubble might finally be bursting.

“Investors started to think that maybe things are a little better here and started to recalibrate where yields should be,” said Michael Brandes, global head of fixed-income strategy at Citi Private Bank.