U.S. crude oil production hit an all-time high last week, according to preliminary government data, in another sign of the resilience of American shale drillers.

The United States produced 9.62 million barrels of oil a day in the week through Nov. 3, the U.S. Energy Information Administration reported on Wednesday. That just slightly topped a high struck in June 2015, just before the oil price crash sparked a more than one-year decline that sent U.S. output to about 8.4 million barrels a day.

To be sure, the weekly figures are subject to revision, but the latest data adds to signs of stubbornly high U.S. output and are likely to weigh on markets. Last week, the EIA’s Petroleum Status Report showed U.S. exports at an all-time high above 2 million barrels a day.

U.S. West Texas Intermediate crude prices initially extended losses on Wednesday after the latest report, which also showed oil sitting in storage in the United States unexpectedly rose last week. Futures recovered slightly but were still trading lower.

U.S. shale drillers, who use advanced drilling methods to unlock oil and gas from rock formations, have frustrated efforts by major oil producing nations to reduce brimming global crude stockpiles and boost prices.

OPEC and other exporters are keeping about 1.8 million barrels a day out of the market in order to end a persistent glut of crude oil.