More than $300 million in copper trades in a span of three minutes were enough to send copper reeling to a one-week low.

From 8:42 to 8:45 a.m. in New York, 4,835 contracts were traded, each covering 25,000 pounds. That was 16 times the 100-day average for that time of day, a spike in volume that extended the red metal’s losses on the Comex.

The metal posted the biggest monthly drop in two years in August and extended declines last week amid concern that an escalating trade war between the U.S. and China will erode demand.