Futures are lower

Stock futures were lower on Tuesday as Wall Street headed for a fourth straight day in the red.

Near 8:57 a.m. ET, Dow futures were down 40 points (-0.22%), S&P 500 futures were down 4 points (-0.23%) and Nasdaq futures were down 12 points (-0.27%).

The last few days have had a decidedly "risk-off" mood in markets with investors buying safer government bonds and ditching stocks.

With the British referendum on its EU membership coming up next week, polls Monday showed the pro-Leave camp is gaining the most momentum in a while.

And that's concerning to investors. On Tuesday, European stocks fell to a three-month low. The yield on Germany's 10-year bond, a benchmark for Eurozone government debt, turned negative for the first time ever amid the buying.

On Monday, the Dow closed down 132 points, or 0.74%.

The Federal Reserve starts its two-day policy meeting in Washington on Tuesday, and its interest-rate decision, projections, and economic forecasts will be released Wednesday.

In economic data, retail sales beat expectations, rising 0.5%. Non-store retail sales (mostly online) have surged in the last few months, and their share of overall sales rose above 10% for the first time.