The US has halted all inbound flights of Afghan evacuees from two main bases overseas for unspecified “health safety concerns”, a move officials warn will have a severe impact on the evacuation operation.

US Customs and Border Protection made the decision on the recommendation of the Centres for Disease Control and Prevention to halt the flights from US bases in Germany and Qatar, according to a government document.

The US has been conducting screening and other processing of evacuees at those two main overseas sites and others after evacuating them from Afghanistan

The halting of the flights is a problem for the United States in part because many of the evacuees already have been at the Ramstein military base longer than the 10-day limit Germany set in allowing the US to use the country as a transit site.

The US document viewed by the AP said the halt would “severely impact” operations at the base in Germany and have an “adverse effect” on the nearly 10,000 evacuees at Ramstein, many of whom have been there more than 10 days and are increasingly fatigued.

The US State Department did not immediately respond to a request for comment.