A company that is one of the largest providers of french fries to Chicago-based fast food giant McDonald’s closed a plant in Washington and laid off nearly 400 employees as sales remain sluggish for the chain.

The cuts at Lamb Weston, the country’s largest french fry supplier, were announced in an earnings call by the company’s president and CEO, according to Fox Business.

The layoffs constitute 375 employees, or nearly 4% of the company’s total workforce.

Although the company also supplies french fries for other restaurants and grocery stores, its business from the fast food industry is the biggest driving factor behind Lamb Weston’s sales.

According to the New York Post, the frequent low-cost meal deals offered by fast food restaurants in an effort to lure customers back to the drive-thru lane have not helped the french fry giant financially.

Industry experts have attributed slowing fast food sales to rising costs on menus of many major chains.