Mr. Mauro said that eight hours after the bacteria were applied to the spill, only 30 percent of the oil remained.

''As far as we're concerned as policy makers, it's time to move forward with bioremediation as a central part of every oil spill contingency plan filed in the state of Texas,'' Mr. Mauro said.

But another expert on oil spills who is familiar with the Texas experiment said it was ''basically inconclusive'' because of problems with flotation devices separating the oil being tested from that of another area. Richard S. Golob, the publisher of Golob's Oil Pollution Bulletin in Cambridge, Mass., said ''it was difficult to determine whether other factors such as wave action or evaporation were responsible for the observed changes.''

At a news conference today, Mr. Mauro and the Texas Water Commissioner, B. J. Wynne, said that while the preliminary results were not conclusive, there was no evidence that the bacteria caused any environmental damage.

Though bioremediation has been used before, most notably to clean rocks washed on shore after the Exxon Valdez spill in Alaska last year, the Mega Borg spill was the first time the bacteria were used in open water.