Alex Azar, secretary of Health and Human Services (HHS), center, speaks while U.S. President Donald Trump, left, and Francis Collins, director of the U.S. National Institutes of Health, listen during a briefing at the National Institutes of Health Vaccine Research Center in Bethesda, Maryland, U.S., on Tuesday, March 3, 2020.

WASHINGTON — Congress is looking for answers on how to respond to the coronavirus. The administration is short on them. And it all adds up to a massive federal government working to solve a problem it doesn't quite understand.

This notion was clear as U.S. health officials leading the coronavirus response were grilled Tuesday in a hearing on the illness held by the Senate Committee on Health, Education, Labor and Pensions.

Questions ranged from how quickly the U.S. will be able to deploy a vaccine (answer: that will take a while), what percentage of people traveling from Canada are being screened for the virus (unclear) and how far germs from the virus spread on a plane (a few rows). Most of the testimony was caveated, and some of it was met with skepticism.

"Do you really believe that one million tests will be available by the end of this week?" Sen. Patty Murray, D-Wash., asked Food and Drug Administration chief Stephen Hahn. Hahn had said in prepared remarks at the onset of the hearing that the administration would be able to achieve that objective.

Murray, whose state has seen nine people die from the illness, is one of many lawmakers who blamed limited testing supplies on allowing the illness to proliferate.

In response to Murray, Hahn later clarified he expects "up to a million tests." He walked the panel through what would need to happen to achieve that goal.

"The company we are working with this have the capacity to develop enough test kits to send out ... and this is a dynamic process — every day I'm hearing from different manufacturers that they can do this — 2,500 test kits by the end of the week. That should give us the capacity in hands of laboratories — once they validate — to perform up to a million tests," he said.

Lawmakers pressed the officials about the potential of drug shortages, given the large portion of the country's supply chain coming from overseas. Hahn said he did not know whether India's decision earlier in the day to limit 10% of its export capacity affected the U.S. supply chain, including essential drugs.