HOUSTON (Bloomberg) — McMoRan Exploration Co., whose partners include Energy XXI (Bermuda) Ltd., said it discovered another layer of oil-and gas-soaked rocks in its Davy Jones prospect, an indication that the biggest find in decades in the shallow waters of the Gulf of Mexico may be larger than previously thought.

McMoRan found a 65-foot column of hydrocarbon- bearing sands after extending the well 340 feet since the initial discovery was announced last week, the New Orleans-based company said yesterday in a statement. The find represents a 48 percent increase in the potential oil-and gas-producing zone to 200 feet.

McMoRan and its partners are exploring rock formations almost six miles underground for reservoirs overlooked by bigger rivals. Davy Jones is in the same geologic layer that yielded BP Plc's Tiber field, which may hold 3 billion barrels of oil, and Chevron Corp.'s Jack discovery.

More tests to determine the porosity of the newly found layer and the potential output from the well are needed, according to the statement.

The other partners in the prospect are Plains Exploration & Production Co., Nippon Oil Corp. and William "Tex" Moncrief, a Fort Worth-based wildcatter.