HOUSTON (AP) — The number of rigs exploring for oil and natural gas in the U.S. rose by six this week to 933.

A year ago, just 424 rigs were active.

Houston oilfield services company Baker Hughes said Friday that 747 rigs sought oil and 186 explored for natural gas this week.

Among major oil- and gas-producing states, North Dakota added three rigs while Alaska, Colorado and New Mexico gained two rigs each. California and Louisiana increased by one apiece.

Oklahoma declined by four rigs and Wyoming was down one.

Arkansas, Kansas, Ohio, Pennsylvania, Texas, Utah and West Virginia were unchanged.

The U.S. rig count peaked at 4,530 in 1981. It bottomed out in May of 2016 at 404.

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