After a few minutes of trading, the Dow Jones industrial average has lost 1 percent, the broad S&P 500 index 1.2 percent and the Nasdaq's technology-heavy composite index 1.6 percent.
Half an hour later, the indices were down between 0.5 and 1.2 percent.
This follows Thursday's fall of between 1.7 and 2.3 percent at the close to mark the worst day in over a month.
The uncertainty surrounding whether AI stocks are significantly overvalued continues. Index-heavy tech stocks such as Nvidia, AMD, Palantir and Tesla have started the last trading day of the week on a decidedly gloomy note.
Another source of concern is how the market will react when economic statistics begin to be released again when the US government has fully reopened after a six-week shutdown – and whether this will in turn lead to the US Federal Reserve refraining from lowering the key interest rate.
