The Department of Homeland Security must improve its COVID-19 response at the U.S.-Mexico border to protect the safety of its workforce, migrants and local communities, a government watchdog has found.

“Without stronger COVID-19 prevention measures in place, DHS is putting its workforce, support staff, communities, and migrants at greater risk of contracting the virus,” investigators in DHS’s inspector general office said in a report Wednesday.

Investigators reviewed DHS efforts to mitigate the spread of COVID-19 among migrants, following a referral about a lack of testing at one Customs and Border Protection location.

The report noted that CBP is not required to test migrants at its facilities, instead relying on local public health systems and nongovernmental organizations to test symptomatic individuals. CBP officials said they lack the “necessary resources” to test migrants and are “not able to maintain proper physical distancing in holding facilities” because of the sheer number of migrants they take into custody.

DHS generally follows Centers for Disease Control and Prevention guidance for COVID-19 prevention, the watchdog report said, but its “multi-layered” testing framework does not require testing at CBP facilities, and Homeland Security’s chief medical officer does not have the authority to direct or enforce testing protocols.

The inspector general’s office recommended that DHS “reassess its COVID-19 response framework to identify areas for improvement” and ensure department agencies coordinate with the DHS chief medical officer and are provided adequate resources to operate safely. DHS concurred with both recommendations.

“DHS is committed to the wellbeing of the communities in which we serve, our workforce, and people in our care and custody,” Jim H. Crumpacker, director of the department’s GAO-OIG liaison office, wrote in a letter included in the report.

The report reflects concerns Republican lawmakers have raised for months about the spread of COVID-19 at the U.S.-Mexico border, which has seen historically high levels of migration this year.

CBP recently reported more than 156,000 migrant encounters in the month of August, a slight drop from July. Most single adults and some families are turned away at the border under a Trump-era public health directive.

In July, Sen. Lindsey Graham, R-S.C., asked Homeland Security Secretary Alejandro Mayorkas for more information about migrant testing at the border amid the spread of the more transmissible delta variant of COVID-19.

“During one of the greatest public health emergencies in recent history, and at a time when illegal crossings are nearing 1.2 million migrants this fiscal year alone, it’s important to understand whether migrants are receiving appropriate COVID-19 testing and screening upon apprehension,” Graham said in a letter to DHS.

And in August, a group of top House Republicans wrote a similar letter requesting more information on COVID-19 protocols at the border, citing reports from a whistleblower that migrants were being released into the country without proper health precautions.