Oilfield services company Baker Hughes Inc. says the number of rigs exploring for oil and natural gas in the U.S. plunged by 35 last week to 1,840.

The Houston firm said Monday in its weekly report that 1,499 rigs were exploring for oil and 340 for gas. One was listed as miscellaneous. A year ago 1,757 rigs were active.

Of the major oil- and gas-producing states, Oklahoma gained four rigs, Ohio rose by two and Louisiana and Colorado were up one each.

California dropped by 17, Texas lost 16 and North Dakota and West Virginia were down three apiece. Alaska, Kansas, New Mexico, Pennsylvania and Wyoming each fell by one.

Arkansas and Utah were unchanged.