The American Hospital Association is warning its members about Vox’s emergency room billing project.

The memo, reported by trade publication Becker’s Hospital Review, came a week after we launched a new effort to bring more transparency to medical pricing by collecting readers’ emergency room bills.

Bob Herman, a reporter with Axois, later shared the entire memo on Twitter:

Earlier this week, Sarah Kliff, a health reporter with Vox Media, a digital media company, announced the launch of a new year-long reporting project on health care prices. Her first area of focus is hospital bills for emergency services and, specifically, hospitals’ use of facility fees. Ms. Kliff is soliciting patient bills from emergency department visits in the U.S. over the past five years (2012 to 2017). An announcement on this project is found HERE. We expect to see stories throughout the year and in 2018. We encourage you and your entire team to be certain that you remain familiar with your organization’s policies and procedures on patient billing, financial assistance policies, and how to talk about them with patients, their families, and the public.

The AHA recommends that members “share and discuss the issues addressed in this advisory with your media staff” and “be prepared to share what steps your organization currently takes to provide transparent billing information.”

The American Hospital Association represents thousands of hospitals across the country. It estimates a membership of “nearly 5,000 hospitals, health care systems, networks, other providers of care and 43,000 individual members.”

Hospitals typically keep their prices private. One study found it was significantly easier to get information from hospitals about how much their parking costs then track down the price of a common medical procedure. When I have tried to conduct interviews with hospital executives about how they set their prices, I find that many are reluctant to comment.

That’s why we launched our project to collect emergency medical bills — to bring more transparency to prices that are typically opaque (and often set very high).

So far, we’ve collected bills from 346 readers who live in 43 states and the District of Columbia. (If you’re curious, the states we haven’t yet received bills from are Arkansas, Delaware, Hawaii, Mississippi, Vermont, West Virginia, and Wyoming.)

We’re looking forward to reporting back on this data and will be writing stories about it, as the AHA memo expects, throughout 2018.

Do you have an emergency bill you’d like to submit? You can share it here — it would be a huge help to us. We’re gathering data on a fee called an emergency room facility fee, which we explained in the first episode of Vox’s new podcast, The Impact.