HOUSTON  — The number of rigs exploring for oil and natural gas in the U.S. dropped by nine this week to 406, another all-time low amid depressed energy prices.

A year ago, 888 rigs were active.

Alaska’s rig count was unchanged this week, but rigs are down to five compared to 10 in the same week a year ago.

Houston oilfield services company Baker Hughes Inc. said Friday 328 rigs sought oil and 86 explored for natural gas. One was listed as miscellaneous.

Among major oil- and gas-producing states, Texas declined by seven rigs, Louisiana was down three and North Dakota, Oklahoma and Wyoming each fell by one.

New Mexico gained two rigs and California one.

In addition to Alaska, Arkansas, Colorado, Kansas, Ohio, Pennsylvania, Utah and West Virginia were all unchanged.

The U.S. rig count peaked at 4,530 in 1981. The previous low of 488 set in 1999 was eclipsed March 11, and has continued to slide.