Several dozen civil liberties groups are pressing the House Judiciary Committee to hold hearings about a domestic surveillance power that Congress authorized in 2015 to end U.S. intelligence agencies’ bulk collection of Americans’ data.

The groups want Congress to investigate whether the government has exceeded the limits imposed by lawmakers on the use of what is known as Section 215 of the Patriot Act. That authority is due to expire in December.

“The information . . . is critical to determine how surveillance authorities are being used and the impact they have on individuals’ rights,” wrote the 39 groups, led by the American Civil Liberties Union, in a letter to Rep. Jerrold Nadler (D-N.Y.), the committee chairman, and ranking Republican member Rep. Douglas A. Collins (Ga.).

“We’re certainly going to look into that,” Nadler said in an interview Monday. He noted that he voted against the original Patriot Act in 2001, with concerns about Section 215 being a key reason for his vote.

In 2015, Congress passed the USA Freedom Act to ensure, among other things, that Section 215 would not be deployed to collect large amounts of data on Americans’ email, phone or other records. It also imposed new limits on two other key national security collection authorities.

The law passed in the wake of controversy over the disclosure by former National Security Agency contractor Edward Snowden that under Section 215, the NSA was collecting millions of “call detail records” daily from major telecommunications providers that the agency could sift through for clues to potential terrorist threats.

Its replacement program, authorized by the USA Freedom Act, involved the U.S. government obtaining records from phone service providers with a court order. The law enabled the agency to collect records of people up to two hops removed from the target. The metadata recorded who called or texted whom, when and for how long, but not what was said.

According to the latest-available data from the Office of the Director of National Intelligence, the NSA in 2017 collected more than 530 million call detail records linked to 40 “targets.” A “target,” according to ODNI, is “the individual, person, group . . . or foreign power” using the phone number in question.

“Because the NSA has failed to disclose” the ultimate number of accounts or devices linked to these 40 targets, as required under the USA Freedom Act, “it is difficult to know how many individuals are likely impacted by such collection,” the groups said.

The call metadata program was reportedly halted last year, according to a congressional aide briefed on the matter. Part of the reason apparently stemmed from what the agency described as “technical irregularities” that resulted in the telecom carriers sending the agency records it had no authority to gather.

The NSA disclosed last June that it had begun “deleting all call detail records acquired since 2015” because of the glitch that resulted in unauthorized collection.

But the agency has not confirmed that the program has been halted, or explained why.

The groups want the committee to press the NSA on these and other matters. “The NSA should also clarify whether it intends to restart the program or has replicated the program under a different authority,” they wrote.

They also want to know why collection has “more than tripled” from 2016 to 2017, and what specific “selection terms” the government uses to gather the records from the companies.