U.S. equities posted the biggest weekly drop since March as investor anxiety grew that trade war with China will escalate and as signs emerge of slower global economic growth.

The S&P 500 fell 4.6 percent in the four trading days through Friday. U.S. markets were closed Wednesday for a national day of mourning to honor former president George H.W. Bush. The Dow sank 4.5 percent to 24,389. The tech-heavy Nasdaq 100 index dropped 4.8 percent.

Stocks have been lurching from rally to rout at an alarming rate. The reasons for the price swings are numerous but largely boil down to concern that rising interest rates and the ongoing trade war will throttle global growth and corporate profits. A dovish turn from the Federal Reserve on interest rates recently sparked the biggest rally since 2011.

Any optimism about trade quickly faded when Huawei Technologies’ chief financial officer, Meng Wanzhou, was arrested in Canada at the behest of U.S. authorities, who allege that Huawei used a firm called Skycom to do business with Iran, breaching sanctions, and that Meng hid the relationship between Huawei and Skycom, according to a lawyer.

The Treasury will sell $39 billion of three-month bills and $36 billion of six-month bills Monday. They yielded 2.41 percent and 2.55 percent in when-issued trading.

— Bloomberg News