The number of U.S. rigs drilling for oil and natural gas plummeted in the past week as an oil price war and uncertainty over the impact of coronavirus drove prices to their largest weekly percentage decline in 29 years.

U.S. benchmark crude lost nearly 11% Friday to close at $22.53 per barrel. It closed the week with a 29% decline, the biggest percentage loss since January 1991.

Brent crude, the global benchmark, fell 20% for the week to close at $26.98 per barrel.

In its weekly report Friday, Baker Hughes said the combined count fell by a net 20 rigs, including 19 that had been seeking oil. That left 772 at work, a decline of 244 from the same week a year ago.

The loss of oil rigs left 664 standing, down 160 from a year ago. The one-rig loss in gas-directed rigs left 106 at work. A year ago, there were 192.

The total of rigs working in Texas was down 11 from a week earlier, to 397. A year ago, there were 497.

The biggest loss was in the West Texas-New Mexico Permian Basin, where drillers took 13 rigs out of service. South Texas’s Eagle Ford Shale lost one.

By state, New Mexico lost five rigs, to 112. Oklahoma’s tally fell by three, to 43. Louisiana was unchanged at 47.

Oil prices have fallen as members of OPEC+ are locked in a price war and promising to flood the market with millions more barrels of crude per day. At the same time, domestic production has been bouncing around record levels for weeks.

The federal Energy Information Administration said earlier in the week that U.S. oil production returned to a record high 13.1 million barrels per day in the week ended March 13.