Drilling service provider Smith International ( SII) said profit tanked 41% in first-quarter, hurt by a decline in drilling demand. The news follows last week's disappointing reports from energy rivals Schlumberger ( SLB), Halliburton ( HAL) and Weatherford International ( WFT). Each posted lower-than-expected earnings. Smith said the quarterly earnings fell to $96.9 million, or 44 cents a share, compared with $174.9 million, or 87 cents, in the year-ago period. Analysts expected earnings of 57 cents a share. Revenue remained flat at $2.41 billion, compared to $2.37 billion a year-ago. North American drilling levels dropped 34%. Shares of Smith fell 7% to $25.83 in afternoon trading, Weatherford dropped 5% to $16.58, Schlumberger declined 3% to $48.23 and Halliburton tipped 3% to $20.08.