The U.S. will begin preventing shipments of protective medical supplies from leaving the country starting Friday as doctors, nurses and other health care professionals working stateside continue to lack the gear they need to shield themselves while battling the novel coronavirus.

Customs officials have started flagging shipments of respirator masks and medical-grade gloves under a recent order from the White House, an official with Customs and Border Protection said Thursday.

The shipments will then be reviewed by FEMA starting Friday, according to new guidance issued by the agency. FEMA will then determine whether to block the supply shipment, directly purchase the products, or allow them to be exported.

Federal officials at FEMA and Customs and Border Protection worked this week to knock down false rumors that the government was seizing products from exporters.

“We are not seizing any personal protective equipment,” Deputy Customs and Border Protection Commissioner Robert Perez said Thursday. “It is just the temporary detention of some shipments that fall within the scope of the presidential memorandum and the [Defense Production Act].”

The protocols will remain in place until August 10, according to the new federal regulation.

According to a FEMA official, the new measures were prompted by the massive demand for supplies created by large orders from countries including India and China, which have also requested personal protective equipment shipments from U.S. based companies.

Under the new regulations, the FEMA Administrator has the authority to grant certain exemptions for “humanitarian” reasons or if exporting a shipment is required to “promote the national defense.”

“By March 2020, the global demand for PPE had grown to unprecedented levels and FEMA and HHS received multiple solicitations for the sale of PPE and other medical supplies,” said a FEMA spokesperson. “Working in conjunction with the U.S. State Department, we conducted a full vetting of the manufacturers who produce and sell PPE, to ensure it complies with regulatory standards.”