A Silicon Valley congresswoman grilled FBI Director James Comey about his agency’s development of a facial recognition database Wednesday – but came up short on absolute assurances that ordinary Americans won’t be swept into the system.

The back-and-forth focused on the FBI’s Next Generation Identification program, which aspires to identify suspects with biometric technology, including facial recognition.

Rep. Zoe Lofgren, D-Calif., peppered Comey with questions about the program's budding image database during a House Judiciary Committee hearing.

Among her raft of inquires, Lofgren pointedly asked if drivers license photographs would be included in the database, currently being built and tested.

“I don’t think so, the Next Gen Identification, as I understand it, is about mug shots,” Comey said. “I think there is some circumstances in which when states send us records, they’ll send us pictures of people who are getting special driving licenses to transport children or explosive materials or something – but as I understand it those are not part of the searchable Next Generation Identification database.”

He volunteered to correct the record if that’s not the case.

Comey was somewhat fuzzy about other details.

Lofgren asked if it’s true that images of 52 million people will be in the face database by 2015, a number asserted by the Electronic Frontier Foundation in April, which also said millions of civil images would be included, based on FBI documents the group acquired.

Comey said he doesn't know if the 52 million figure is accurate.

“I saw some of the same media,” he said, “and that’s what led me to ask my folks: So what’s the deal with this? And the explanation to me was the pilot is mug shots, because those are repeatable, we can count on the quality of them, and they’re tied to criminal conduct, clearly, and so there was not a plan and there is not at present where we are going to add other non-mug shot photos. But again, if I’ve got that wrong I'll fix it with you.”

Lofgren pressed further.

“It’s my understanding that the contractor who is building this Next Generation database, a company called MorphoTrust, also built the State Department facial recognition database, which contains 244 million faces," she said. "Will your Next Generation Identification system be capable of importing the State Department records or searching the State Department records?”

Comey wasn’t sure.

“I don’t know, I have not heard of that as either a current capability or an intended capability – I’ll get back to you,” he said.

American police made 12,196,959 arrests in 2012, one every two seconds, according to FBI data released in September 2013, meaning mug shot-driven database growth alone could be significant.