Benchmark Treasury yields dropped to their lowest level since late August as investors shunned risk in favor of perceived safety of U.S. government debt on Tuesday. The 10-year Treasury note (10_YEAR) yield, which falls as prices rise, was down 4 basis points on the day at 2.387%. The last time the yield closed below that level was Aug. 29, according to Tradeweb.

Here’s what is fueling the risk-off trade:

Investors are also preparing for a trio of U.S. Treasury note auctions this week, which kick off with a $27 billion sale of 3-year notes (3_YEAR) , part of $61 billion in total sales.

Strategists at Nomura Securities said they expected “decent” demand at the auction, but noted that “the 3-year outperformed on the curve during Monday’s rally, which may have crowded out some buy-the-dip demand.”

The 30-year bond (30_YEAR) yield dropped 3 basis points to 3.098% and the 5-year note (5_YEAR) yield fell 3 basis points to 1.663%.