The government last year searched for the phone records of fewer than 300 people in a database containing tens of millions of Americans’ phone records, intelligence officials said Saturday in a statement to Congress.

The figure’s release is part of a push by officials to allay privacy concerns following recent disclosures of National Security Agency surveillance programs that collect massive amounts of data in an effort to thwart terrorist attacks.

The phone records program, highly classified until recently, dates to 2006 and is authorized under a still-secret interpretation of Section 215 of the Patriot Act. Under that “business records” provision of the Patriot Act, the government can seek an order from a special surveillance court to direct phone companies to turn over all call detail records on a daily basis as long as they are relevant to a foreign terrorist investigation.

The “metadata” collected includes phone numbers dialed and length of call but not call content, caller identity or location information.

“Only a very small fraction of the [information] acquired under the program is ever reviewed,” the statement said, noting that the government may not query the database for a particular phone number unless it has “reasonable suspicion” that the number is related to a specific foreign terrorist group.

Nonetheless, the amassing of the database — code-named MAINWAY — from the records of so many Americans who have no conceivable tie to terrorism has stirred deep concerns from a number of lawmakers as well as civil liberties advocates. They were not mollified by the release of the number.

“Under the standards of Section 215, they should not be able to have that large database of phone records in the first place,” said Sharon Bradford Franklin, senior counsel of the Constitution Project, a civil liberties organization. “The fact that they’re applying self-imposed restrictions — to have reasonable suspicion to search — doesn’t cure the problem of the over-collection.”

The government “does not indiscriminately sift through the telephony metadata acquired under this program,” the statement said. “This program was specifically developed to allow the [government] to detect communications between terrorists who are operating outside the U.S. but who are communicating with potential operatives inside the U.S.”

The statement repeated officials’ assertions that the NSA surveillance programs have contributed to the disruption of dozens of terrorist plots in the United States and more than 20 countries. But some lawmakers said they have seen no evidence that the phone records program has contributed to disrupting so many plots.

“When the intelligence community asks for a program that touches on the privacy rights of a significant number of Americans, they have an obligation to lay out how it provides unique value in terms of American security,” Sen. Ron Wyden (D-Ore.) said in an interview Friday. “I don’t think that’s being done.”