Federal officials were "cautiously optimistic" Saturday that one of the largest concentrations of Texas refineries near Houston escaped serious damage as Hurricane Rita (search) veered farther to the east.

But the Energy Department (search) said it was too soon to assess the impact of the storm on a cluster of refineries in the Port Arthur-Beaumont (search) area that caught the direct impact of the hurricane as it came ashore.

Based on computer modeling and initial reports, department spokesman Craig Stevens said, "We're cautiously optimistic about (the Houston) ... region" and "that the petroleum supply will be OK."

"But we really need to look at the Port Arthur region and other areas directly impacted. ... It may still be two or three days before we get a sense of the actual picture," he said.

The Houston and Texas City area has nine refineries with a combined capacity to process 2.3 million barrels of crude a day. Four refineries in Port Arthur and nearby Beaumont have a 1.7 million barrel a day capacity.

Sen. Kay Bailey Hutchison (search), R-Texas., was told Saturday by some Port Arthur area officials that they were concerned about flooding at some of the refineries there, according to the senator's spokesman.

Hutchison said on CBS' "Early Show" that she thought the huge ExxonMobil (search) refinery in Beaumont with a capacity of 348,000 barrels a day, "was probably OK." She said she was unsure about three refineries in Port Arthur closer to the coast.

Energy Secretary Samuel Bodman (search) has said the government stands ready to provide additional oil from the government's Strategic Petroleum Reserve should refiners start up as the storm subsides.

About 90 percent of the Gulf oil production has been shut down either because of damage from Hurricane Katrina three weeks ago or because of Rita.

Along the Texas coast, 16 of 21 refineries with combined daily capacity of about 4 million barrels a day were closed because of the impending hurricane. That represents 23.5 percent of the nation's total refinery capacity.

With refineries closed, most pipelines carrying crude or refined products from the Texas region also were shut, reducing the flow of gasoline, diesel and jet fuel into the Midwest, the department said.

Meanwhile, three nuclear power plants that had been put on alert because of Rita continued operating, escaping the storm path by 100 miles, the Nuclear Regulatory Commission said Saturday.

The South Texas Project (search) twin reactors near Bay City, Texas, were not affected. One or the units was at 100 percent operation; the other continued a previously scheduled shutdown for maintenance.

Two reactors owned by Entergy in Louisiana — one near Baton Rouge and the other 20 miles west of New Orleans — were unaffected by the storm and continued full power operation.