Oilfield services company Baker Hughes Inc. says the number of rigs exploring for oil and natural gas in the U.S. declined by 18 this week to 619.

The Houston firm said Friday 498 rigs sought oil and 121 explored for natural gas amid depressed energy prices. A year ago, 1,543 rigs were active.

Among major oil- and gas-producing states, Texas declined by 13 rigs, New Mexico, four; Louisiana, three; and Kansas, North Dakota and Pennsylvania, one apiece.

Alaska and Colorado each increased by two rigs and Oklahoma was up one.

Arkansas, California, Ohio, Utah, West Virginia and Wyoming were all unchanged.