“It’s like smoke and mirrors or a shell game,” said Joanne Belanger, Lexington health director. “We have a license for this particular restaurant, but they also run six or seven other things on the side.”

Many consumers who browse and order groceries online through third-party providers like Grubhub probably don’t give too much thought to where their wings and burgers are coming from.

But the question is nagging at some health inspectors amid a nationwide explosion of online-only grocery stores.

No one knows how many such operations are going on in Massachusetts or across the country as there is no central entity tracking them. But authorities from local health officials to the Food and Drug Administration are concerned and struggling to catch up. At the same time, restaurant industry leaders and some regulators say these virtual food hubs are safe and pose no more risk than brick-and-mortar establishments.

A recent survey conducted by the National Restaurant Association found that about 40 percent of restaurant operators said they expect to open more such virtual businesses this year, in an industry already estimated to be a $43 billion market .

“Our regulations have not kept pace with technological changes,” said Timothy McDonald, Needham’s health director. “I think we’re just trying to figure out how to manage this in a safe and responsible way.”

The inspectors’ primary concern is how these restaurants will affect their ability to track foodborne illnesses. Such cases are already notoriously difficult to trace, as the process relies on people’s memories of what and where they ate. The growth of virtual restaurants is likely to make this process even more complex, inspectors say.

“If we think a restaurant isn’t making burgers and there’s a foodborne illness that’s affecting burgers, and we’re like, ‘There’s no way this can come of this [that restaurant] because they don’t make burgers,” McDonald said.

Inspectors are also concerned about an increased potential for so-called cross-contamination events, where consumers are unknowingly exposed to ingredients to which they are allergic. This can happen, according to inspectors, when kitchen workers who are used to preparing food from the menu in a brick-and-mortar restaurant may not realize that they need a different storage and preparation process for all the virtual operations taking place at the same time.

“I don’t want to take business away from any place, but I also want to make sure there’s no cross-contamination,” said Jeffrey Stephens, Leominster’s health director.

Virtual restaurants, sometimes called ghost kitchens, only exist online and can take many forms. Typically, a brick-and-mortar restaurant opens several virtual restaurants with different names and menus and prepares the food in their existing kitchen. These virtual brands only appear online and are visible to customers ordering through takeaway and delivery apps.

With little guidance from the state Department of Health, which does not track virtual food surgeries, the Massachusetts Health Officers Association recently asked its Academic Public Health Corps, made up of public health students and experts, to investigate how prevalent the phenomenon is in Massachusetts, how diverse communities inspect and license them and what harm, if any, they can do.

They hope to have some answers later this summer.

The National Association of County and City Health Officials said in regions where they’ve heard from local health officials, these virtual restaurants must obtain separate permits and inspections — if the central location for food preparation can be found.

“But the difficulty lies in identifying the operations,” the association said in a statement.

The Food and Drug Administration held a three-day summit last fall entitled “Ensuring the Safety of Food Ordered Online and Shipped Directly to Consumers” to address safety concerns surrounding virtual restaurants.

The agency said in a statement it is still studying all the different versions of online grocery stores, the potential safety risks and “what the regulatory community can do together with the FDA to address the gaps.”

However, industry leaders say virtual restaurants are safe and do not require separate regulations or permits.

“Restaurants have always offered specials that aren’t on the menu, so how else?” said Bob Luz, president of the Massachusetts Restaurant Association.

“If I carry a second menu from Bob’s Burgers, say I now carry Ann’s Chicken Sandwiches, it’s no different. It’s all food,” he said.

Robert Earl, chief executive of Earl Enterprises, which owns Bertucci’s, Planet Hollywood and several other chain restaurants, as well as a number of virtual establishments, said adding new foods to a menu, or even a new virtual restaurant, shouldn’t have any impact on a health inspection that is expanding focused on whether food is properly stored and refrigerated, whether the place is clean and the facility has the right equipment.

“If [an inspector] I would like some prior knowledge that virtual brands exist, I have no problem with that,” Earl said. “All they have to do when they walk through the door…is ask that. Nobody hides it.”

Health inspectors in Boston have become aware of virtual restaurants for several years, said Lisa Timberlake, spokeswoman for the city’s Department of Inspection Services. If the brick-and-mortar parent company is properly licensed and using the same staff to prepare virtual restaurant orders, the department sees no cause for concern, she said.

“As long as it comes from the same restaurant, whatever they want to run online, it still goes back to that core business,” she said.

According to Timberlake, the health department has reviewed fewer than five virtual restaurants in recent years and found no violations of health codes. Boston has no plans to prosecute or regulate online restaurant brands, she said.

“All these new, innovative ideas and business models are popping up all the time,” Timberlake said. “We want to work with people”

The Chelmsford Health Department discovered last year that local Bertucci’s operated six virtual restaurants and, after discussions with the company and the local facility, added the names of the virtual operations to Bertucci’s permit and treated them as one business.

“It worked out well,” said Donna Greenwood, a Chelmsford inspector. “We had no concerns, problems or complaints.”

But the Needham Health Department recently ran into a significant problem: a Thai restaurant that the department closed this spring because of repeated health injuries has opened a virtual Thai restaurant under a new name.

“The concept of restaurants circumventing lockdown through online technology is concerning,” Needham’s McDonald said.

In Lexington, where the inspector recently stumbled upon the company’s virtual operations after finding french fries on the floor and other cleanliness issues, the health department sent a notice to Bertucci to halt the virtual portion of its local business until the City could test it and issue permits.

“Everyone will be looking at this through their own lens and training,” said Belanger, Lexington’s director of health. “If there’s a way, great, the state should show us and make it safe for the consumer.”

Kay Lazar can be reached at kay.lazar@globe.com. Follow her on Twitter @GlobeKayLazar. Anissa Gardizy can be reached at anissa.gardizy@globe.com. Follow her on Twitter @anissagardizy8 and Instagram @anissagardizy.journalism.