Tropical Storm Don is moving through the Gulf of Mexico and is expected to approach the southeastern coast of the U.S. state of Texas on Friday.

The U.S. National Hurricane Center in Miami says the storm is moving west-northwest at about 26 kilometers per hour, with sustained winds of 75 kilometers per hour.

Forecasters expect the storm to make landfall along the Texas coast late Friday or early Saturday.

A tropical storm warning is in effect for parts of the southern Texas coast .

Tropical Storm Don is the fourth named storm of the Atlantic hurricane season.

Some energy companies with oil rigs and other facilities in the Gulf of Mexico have begun evacuating non-essential workers.

Gulf of Mexico oil refineries are responsible for almost one-third of U.S. oil output.