The Consumer Price Index, which measures how quickly prices are going up in the U.S. economy, rose at a faster than anticipated 2.1 percent in January compared to a year ago, triggering fears of another rocky run on Wall Street.

The monthly Labor Department report on the price of everything from gas to groceries was closely watched Wednesday, with Wall Street investors suddenly very concerned about inflation.

The stock market sell-off earlier this month that caused the Dow to fall over 1,000 points in a single day began after a Labor Department report showed wages grew at a better-than-expected pace in January.

Now another key gauge of inflation — CPI — is showing a similar upward trend.

Inflation around 2 percent is still very low, but Wall Street traders fear that this could be the beginning of a quick run up in wages and prices.

In a worst-case scenario, consumers and businesses might start pulling back on spending as they see prices rise rapidly in the coming months (or years). On top of that, the Federal Reserve typically responds to higher inflation by hiking interest rates, ending the easy money days that have fueled a 9-year stock market boom.

“Stock market valuations are high. People are on edge and looking for an excuse to sell,” said Chris Zaccarelli, chief investment officer of Independent Advisor Alliance. “The fact that interest rates could move up so quickly is a legitimate reason for the market to get spooked.”

In recent years, investors put their money in riskier stocks since they were earning so little in interest at the bank or from bonds. But if inflation returns in force and the Fed hikes interest rates, it could cause Wall Street to redo the playbook. As bond yields rise, investors are likely to jump out of stocks and into bonds.

As the Fed lifts rates, companies and individuals also tend to borrow less, another potential damper on the economy.