Shares of

Teco Energy

(TE)

were taking a beating Friday as concerns over the company's credit situation prompted Merrill Lynch to lower its investment rating on the stock.

The shares were down $3.33, or 24.7%, at $10.17 in recent trading on the

New York Stock Exchange

. Year-to-date, the stock has tumbled nearly 75%.

The Tampa, Fla.-based utility concern said Thursday its $350 million credit line, which expires on Nov. 13, has been largely drawn to cover the pending maturity of $236 million in debt that a new bond offering was targeted to cover. Subsequently, Merrill downgraded the stock to sell from a neutral rating, citing heightened liquidity risk.

"With the expiration of the $350 million bank line on Nov. 13, there is a reasonably high risk that the company will not be able to renew the facility," analyst Steve Fleishman wrote in a research note. "Our main concern is that with limited access to capital markets and bank renewals, Teco's credit ratings could come under pressure."