Oil and gas stocks plunged at the opening of trade today pulled lower by Valero Energy Corp.’s announcement yesterday that is expecting a net loss of 50 cents per share for the second quarter of 2009.

Crude oil prices were also increasing pressure on the energy sector, trading down 88 cents to $67.67 a barrel in the New York Mercantile Exchange by 9:55 a.m.

The Amex Oil Index decline 3.71 percent to 971.80 points, while the Amex Natural gas Index dropped 3.44 percent to 439.57 today. Philadelphia Oil service index declined 5.19 percent to 174.46 points.

Valero shares declined as much as 16 percent to $18.66 in early Wednesday trading.

Valero said yesterday the loses expected for this quarter are due to an extended downtime at its refineries , weak sour crude oil discounts and lower diesel margins.

Because of low demand for gasoline in the U.S. due to the economic recession, Valero's shares price has dropped to the lowest in five years during recent months. Also the company has abandoned upgrades to its plants.