Standard & Poor's Ratings Services is warning banks with high levels of exposure to the energy industry to think twice before ramping up their lending in other sectors.

On Tuesday, the ratings agency downgraded its credit ratings one notch for four banks: BOK Financial in Tulsa, Okla., Cullen/Frost Bankers in San Antonio and Comerica and Texas Capital Bancshares in Dallas. Standard & Poor's also lowered its outlook on BBVA Compass in Birmingham, Ala., to negative from stable, which could serve as the prelude to a future cut to its credit rating.

The ratings shift mainly reflects concerns S&P had about the higher loan losses these banks could incur within their energy loan portfolio as oil and gas prices continue to fall. But the ratings agency is also concerned that economies in some energy-dependent states could weaken, thus making loans to other sectors more risky.

"We are also wary of strategies that some banks may execute to aggressively grow their loan portfolios in other loan segments, such as [commercial real estate], in order to offset contraction in their energy loan portfolios," the ratings agency said.

BOK Financial's and Comerica's credit ratings were both lowered to BBB-plus from A-minus, Reuters first reported. Texas Capital Bancshares was dropped to BB-plus from BBB-minus, while Cullen/Frost's rating was pulled down to A-minus from A.

Dick Evans, the departing chairman and chief executive at the $28 billion-asset Cullen/Frost, rejected the premise that Texas overall will suffer because of the energy downturn. He said that both the state's economy and the bank's loan portfolio "are very diversified."

As for the bank's energy portfiolio, Evans said he expects losses to be contained. "We don't bank the energy business; we bank individuals in the energy business," he told American Banker by phone Wednesday. "We're close to our customers and we're working with them."

Other banks remained similarly resolute. Reacting to the S&P downgrade, a spokesman at the $72 billion-asset Comerica harkened back to the company's "30-plus-year history and extensive knowledge of energy lending." And a spokeswoman for the $18.9 billion-asset Texas Capital said that it's on the company now to prove the analysts wrong.

"We believe our underwriting standards will differentiate us from others and it is our responsibility to demonstrate in coming quarters the conclusions reached were unwarranted," she said in an email.

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