The number of rigs searching for oil and natural gas in the United States fell by seven to 1,225 during the week ending May 18, according to oil services firm Baker Hughes. Last year the number of U.S. rigs was 841, Baker Hughes said. Meanwhile, the number of rigs exploring for oil and gas in Canada gained 24, compared to 182 last year. The number of rigs in the U.S. Gulf of Mexico fell by four to 160, compared to 135 a year ago.