Laboratories around the country are now facing potential shortages of key materials and chemicals needed to run tests for the novel coronavirus, as cases spread to more than two-thirds of the states and the global pandemic strains testing resources even further.

Some lab directors say they are already beginning to run low of the supplies needed to extract RNA from nasal swabs, a crucial initial step that is separate from the millions of test kits that the federal government has promised to ship to every state. Others say they are weighing whether to borrow some materials from other research labs that aren’t involved in creating or running coronavirus tests.

And some lab directors are worried about the future availability of the reagents, or chemical ingredients, used in the tests themselves. Several labs have also said that they have had trouble getting virus samples that are needed to validate the tests to make sure they are properly identifying positive samples.

Public health officials and health care providers have clamored to get enough tests following a botched rollout of testing kits by the Centers for Disease Control and Prevention — and a delay by the Food and Drug Administration in allowing independent labs to develop their own test — that led to weeks of delays in detecting the spread of the virus in the country.