On Jan. 9, clothing manufacturer Twin Hill stated the uniforms it provided American Airlines Group Inc. (AAL) employees were safe. It was the first time Twin Hill commented publicly about the complaints.

In a letter to the Association of Professional Flight Attendants (APFA), the manufacturer said it is trying to schedule a visit to American Airlines’s uniform distribution center and that it offers non-wool alternate uniforms.

Since the new uniforms debuted in September 2016, American Airlines employees have complained of skin irritations, headaches and hives, reports the Dallas News.

In December 2016, the APFA called for American Airlines to recall the Twin Hill uniforms. The Dallas News reports that around 2,200 employees have complained about the uniform, and the majority of the complainants are flight attendants. (See also: Erin Brockovich Rumored to be Interested in American Airlines Uniform Issue.)

In response to the union’s complaint, American Airlines said both it and Twin Hill had tested the uniforms in independent laboratories, and the uniforms appeared safe to wear.

According to the Dallas News, Diego Louro, a spokesman for Twin Hill said, “We want to resolve this problem. As far as we’re concerned, we have yet to see any kind of evidence suggesting there is something [wrong] within our garments. If there is, we want to get to the bottom of it.”

The uniforms were distributed to over 70,000 frontline employees at American Airlines. It was the first time since American Airlines’s 2015 merger with US Airways that all employees were able to wear the same uniform, says the Dallas News. (See also: American Airlines & US Airways Merger: It Matters!)

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