Staff and aides to D.C. Mayor Muriel Bowser are using the message service WhatsApp to communicate, a practice that’s becoming more common among public officials across the country. But it’s also raising concerns among open-government advocates over public business being conducted on a private app—and largely beyond the reach of laws requiring that documents and records be preserved and made available to the public and press upon request.

The exact scope of WhatsApp use among the mayor’s staff remains unclear. But one person with direct knowledge of the situation who asked not to be identified said it is “commonplace” for communication between managers and employees, both individually and in groups. Much of that communication happens during the day and touches on official government business and functions.

“We communicate using a variety of methods to accomplish our work in an expeditious manner,” said Bowser’s office in an emailed statement.

WhatsApp, which is owned by Facebook, is a new class of app-based messaging services that allow users to send text messages, place audio and video calls over the internet, and share documents. Similar services include different degrees of encryption and anonymity, with some—like Signal, Confide, and Telegram—destroying messages after a specific amount of time.

Their ease of use has made them widely popular; WhatsApp alone has 1.5 billion users worldwide. And that includes government officials and employees, who can take advantage of app’s functionality the same way any private person can.

But unlike physical paperwork government workers create or emails they send over official servers, the messages sent via WhatsApp and similar services are not directly available to the press or public, and may not be subject to open-records laws—especially if a public official is using the app on a personal phone. And that has raised alarm among open-government advocates.

“The backbone of open government and of good government is public records. And when officials move these activities into these spaces that weren’t designed for them, record-keeping might be inherently disabled,” says Alex Howard, who has focused on the intersection of technology and government at the Sunlight Foundation and now with an organization called Demand Progress.

Every technological advancement has posed some type of challenge to open-records laws. In 2012, the D.C. Council was sued over its refusal to turn over official correspondence done via members’ personal email accounts, though it reversed course a few months later. And in 2013, D.C. turned down a request for copies of text messages sent from then-mayor Vincent Gray’s city-funded cell phone.

More recently, White House Senior Advisor Jared Kushner was accused of using WhatsApp to speak to foreign contacts, potentially violating the federal law requiring all public records to be maintained. And former Missouri Gov. Eric Greitens, a Republican, admitted last year that he used Confide, which deletes text messages after they are received, to communicate with his staff.

Thomas Susman, president of the D.C. Open Government Coalition, says public officials and employees sometimes will assume that informal conversations done over messaging services or private emails are not actually public record—even though they likely are.

“If the communication on WhatsApp is, ‘What did you think about the presentation on the new lottery contract?’ that’s public business,” he says.

And he has strong reservations about city officials using WhatsApp for public business, especially since public access to their messages through open-records requests is significantly more limited than if they traded emails on an official account.

“For executive officials to use WhatsApp is such a flagrant effort to avoid public disclosure. If the mayor doesn’t clamp down on it then I’m confident there will be a legal challenge to that because the public’s business should be done in a medium that’s available for public access,” he says.

For Howard, what’s needed is for governments across the country to educate civil servants more proactively on what’s permitted and what’s not, and to strengthen open-records laws where necessary to more closely match advances in technology.

“This isn’t a surprise to see city councils or civil servants using a private messaging service. This is something we’ve seen for a long time. The key is for legislatures to say, alright, there’s an expectation that if you use another service for public business you’ll archive it, if it can’t be archived then you shouldn’t use it,” he says.

Last year, then-Kansas Gov. Jeff Colyer, a Republican, followed that guidance, signing an executive order requiring employees in his office to use their official email accounts for state business. But in other states—including Kentucky, Arizona, and Virginia—bills have been introduced that would have exempted personal social media accounts and phones from open-records requests. Open-government advocates strongly opposed those measures, and none moved forward.

Susman believes that D.C.’s current open-records law can be applied easily enough to private email, text messages, and services like WhatsApp: If someone is going to use them for public business, they need to find a way to make a record available, whether by sending a copy of an email to their official account or taking screenshots of their WhatsApp messages. Bowser’s office did not respond to questions as to whether any guidance is provided to staff on archiving messages sent over WhatsApp.

But as for messaging services like Signal and Confide, which delete messages upon receipt, Susman says stronger measures may be needed.

“I don’t see much difference between using a communication method that destroys the communication after you’ve read than to take a piece of paper that you’ve received for official business and running it through the shredder or deleting an email and deleting it from the hard drive so it can’t be recovered,” he says.

This story originally appeared on WAMU.