The massive drop, recorded as shares opened in New York on Thusday, followed an 800-point plunge on Tuesday.
This brings the Dow’s total loss to more than 1,400 points in just two days.
Wednesday’s market was closed due to the funeral of President George HW Bush.
The losses are being blamed on rising fears of a trade war between Washington and Beijing, fuelled by the detention of a Chinese executive in Canada.
Meng Wanzhou, chief global finance officer of Chinese telecoms company Huawei, is currently being held by Canadian authorities.
China has demanded her release – but until that is done, market uncertainty is likely to remain.
This is a breaking story – more to follow.