LONDON—Tullow Oil PLC's shares fell as much as 3.3% Tuesday morning after the U.K.-listed company said it failed to find oil or gas at a test well off Ghana's coast.

The Dahoma-1 exploration well was the first of 12 planned deep-water exploration wells, the company said. The well was classified as high-risk and was used to evaluate the potential for oil in the area of the West Cape Three Points license, Angus McCoss, exploration director at Tullow Oil, said.

"We now look forward to incorporating the data from this well and to pursuing the largely independent and considerable remaining prospectivity in the West Cape Three Points block which we will be drilling through 2010," Mr. McCoss said.

The company's shares were recently down 2.6%, making it the worst performer among FTSE 100 stocks. The FTSE 100 index in London was up 0.4%.

Analysts at Evolution Securities said the results could hurt Tullow's shares more than warranted if investors become concerned that the test well augurs poorly for the area.

Tullow will now move the rig at Dahoma-1 to drill the Mahogany-5 well. Tullow's next high-impact wildcat is Owo-1, in the Deep Water Tano license off the coast of Ghana, which will be drilled in June.

Tullow has a 22.9% interest in the West Cape Three Points license. Kosmos Energy, the operator, and a subsidiary of Anadarko Petroleum Corporation own 30.88% each in the license while the E.O. Group owns 3.5%, Sabre Oil & Gas 1.85% and the Ghana National Petroleum Corporation owns a 10% carried interest in the license.

In the Deepwater Tano license, Tullow is the operator with a 49.95% equity stake. Kosmos Energy and Anadarko Petroleum each own an 18% stake in the license while Sabre Oil & Gas owns 4.05% and the GNPC owns a 10% carried interest.