Whataburger is exploring possibilities that could include a sale to a private equity firm or financial investor, the company said.

The San Antonio-based fast food chain confirmed the possibility to Reuters earlier this month. Whataburger also confirmed Thursday that the company had hired Morgan Stanley, the multinational investment bank and financial services company, the San Antonio Business Journal reported.

"Our company is growing and is always attractive to investors, and we've brought in Morgan Stanley to help us explore our options," Whataburger said in a statement provided to the Business Journal. "We have always evaluated the opportunities that can accelerate growth and maintain the success of our brand, and we will continue to do so in the future."

Whataburger operates more than 800 locations nationwide, according to its website; most of them are in Texas.

Citing a source, Reuters reported that the privately held company's value could top $6 billion.

The Business Journal reported that Whataburger posted sales of more than $2.2 billion in 2017, citing trade publication QSR. The figure placed the chain 22nd among QSR's 50 biggest limited-service restaurants based on sales, above others such as Hardee's, Carl's Jr. and Five Guys.