HOUSTON (AP) — The number of rigs exploring for oil and natural gas in the U.S. increased by 18 this week to 712.

A year ago, 619 rigs were active.

Houston oilfield services company Baker Hughes Inc. said Friday that 566 rigs sought oil and 145 explored for natural gas this week. One was listed as miscellaneous.

Texas increased by nine rigs, Oklahoma was up by five, New Mexico increased by four, Louisiana was up by two and Alaska and North Dakota each increased by one.

Colorado decreased by three rigs and Arkansas and West Virginia each were down by one.

California, Kansas, Ohio, Pennsylvania, Utah and Wyoming were all unchanged.

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