The Food and Drug Administration has “more than 200 food investigators” on the job “not counting support staff and supervisors” out of about 550 total professionals “when the agency is fully operational,” according to Commissioner Scott Gottlieb.

In a “tweet” Monday, the FDA commissioner said he was responding to questions about staffing levels for FDA’s Office of Human and Animal Food Operations. It was one of the most detailed statements about food safety staffing that Gottlieb has made since the partial government shutdown began on Dec. 22.

In a follow-up tweet, Gottlieb expressed his appreciation.

“We’re deeply grateful for the FDA professional staff that continues carry on this mission unpaid, while also incurring expenses on their personal government credit cards for travel,” he wrote. “We’re doing everything we can to support hem as they protect American consumers.”

FDA’s fellow food safety agency, the U.S. Department of Agriculture’s Food Safety and Inspection Service (FSIS) continues to deploy most of its workforce of nearly 10,000, mostly at the meat and poultry establishments that are required by federal law to have continuous inspection services for their food production to continue.

FSIS inspectors must be on the job for meat and poultry to be deemed fit for human consumption.

While FDA is responsible for regulating about 80 percent of the nation’s overall food production, it is not required to provide continuous inspections. It an FDA-regulated facility isn’t high risk or seen as a problem, it is not usual for there to be several years between inspections.

The FDA commissioner’s tweets come as he is reportedly becoming concerned about the long-term impact of the government shutdown.

Congress has passed legislation that guarantees federal government employees will all get paid just as soon as a deal is reached to re-open the parts of the government with funding lapses. But congressional leaders and the White House are stilling talking past one another instead of engaging each other in real negotiations.

The federal Centers for Disease Control and Prevention in Atlanta escaped the partial shutdown with funding from the normal appropriation process. It continues to investigate multi-state outbreaks of foodborne illnesses. Detection of foodborne illness falls first on the nation’s 2,700 state and local health districts, which also are not affected by federal closures.