A spike of coronavirus cases at two of General Motors’ key factories has put the United Auto Workers (UAW) union on high alert.

Since GM resumed production at its Arlington Assembly, Texas plant in late May, a total of 22 cases of coronavirus have been confirmed. The facility handles production of GM’s full-sized SUVs. At the Wentzville Assembly site in Missouri, responsible for the company’s mid-sized pickups and full-sized vans, there have been 12 confirmed cases since production resumed in mid-May.

“If we continue to see the number of cases trend upward, the union would have to request a shutdown of the plant again so that it can be cleaned and workers can get tested,” a person with knowledge of union leadership told the Detroit Free Press. “It’s a concern.”

GM has a policy of not confirming the numbers of coronavirus cases in its plants.

The two production sites employ a touch over 9,000 people and while only a small percentage have tested positive for Covid-19, some workers at the facilities say they are afraid of contracting the virus because of how contagious it is.

“The UAW is watching very carefully how these health and safety factors are impacting different plants and we are in a continual dialogue at all levels,” UAW spokesman Brian Rothenberg added. “Health and safety for all members is our priority.” He added that the union is “constantly in discussions” with the automaker.

Read Also: Coronavirus Pandemic Forced GM To Become More Efficient, Lower Its Costs

The union cannot order a plant to be closed or stay open and must engage in discussions with the company to develop strategies to handle any potential issues.

GM spokesman David Barnas reached out to the Detroit Free Press late last week saying no changes are planned at either of the factories.

“Many of the same steps we follow inside our plants can help keep people safe when they’re not working, and that includes staying home if you’re not well, social distancing when you leave home, frequent hand-washing and the use of masks,” he said.