Two Arizona men have pleaded guilty in a failed insurance scheme to blow up chemical tanks near a huge naval base in February, an incident that heightened fears over terrorism during the Persian Gulf war.

Joseph Wayne Openshaw, an engineer, and Cecil Howard Ross, a power plant contractor, entered the pleas Friday in a deal with prosecutors.Openshaw, 37, of St. Johns, Ariz., and Ross, 31, of Glendale, Ariz., pleaded guilty to conspiracy. Openshaw also pleaded guilty to one count of wire fraud.

The pleas in U.S. District Court came a day after admitted mastermind Charles Edward Gresham pleaded guilty in the Feb. 4 attempted bombings.

Gresham, 57, of Ellicott City, Md., pleaded guilty to conspiracy, making an illegal bomb and attempting to bomb a facility used in interstate commerce.

He was behind on rent payments for a tank at Allied Terminals Inc., investigators said. The tank, full of sodium sulfide solution Gresham owned, was among those fitted with pipe bombs at the storage farm about 10 miles from Norfolk Naval Base.

The attempted bombings raised fears of war-related terrorism and prompted the evacuation of thousands of residents within a mile of the tank farm. Authorities safely detonated and dismantled the clusters of bombs.

According to an FBI affidavit, Gresham insured the chemical solution for $2.7 million. After expenses, the insurance profit was estimated at $1 million, the affidavit said.

The FBI said Openshaw's name appeared on a bogus sales contract that was used to obtain the insurance policy. Ross was listed in the affidavit as having sent a drawing of a pipe bomb to Gresham after a meeting of the three men in January.