The Environmental Protection Agency barred reporters from The Associated Press, CNN and other media organizations from attending a national summit on water contaminants, led by EPA Administrator Scott Pruitt on Tuesday morning. One reporter says she was "forcibly removed" from the event.

CBS News, Politico, The Wall Street Journal, the Hill and a handful of other news organizations did attend the kickoff of the EPA's two-day summit that included representatives from 38 states from around the country to discuss polyfluoroalkyl substances — chemical water contaminants widely used in commercial substances found to have adverse health effects in lower quantities than initially recognized by the EPA.

E&E News tweeted that its reporter Corbin Hiar tweeted that reporters from his outlet, The AP, and CNN had been "selectively shut out" from covering the event. "This morning's PFAS Leadership Summit at @EPA headquarters is open to the press... just not to reporters from @EENewsUpdates, @AP or @CNN. We've all asked the agency's press office why we're being selectively shut out and have gotten no responses," he wrote.

This morning's PFAS Leadership Summit at @EPA headquarters is open to the press... just not to reporters from @EENewsUpdates, @AP or @CNN. We've all asked the agency's press office why we're being selectively shut out and have gotten no responses. — Corbin Hiar (@CorbinHiar) May 22, 2018

EPA spokesman Jahan Wilcox told CBS News in a statement that their exclusion was a matter of room capacity.

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"This was simply an issue of the room reaching capacity, which reporters were aware of prior to the event," he said. "We were able to accommodate 10 reporters, provided a livestream for those we could not accommodate and were unaware of the individual situation that has been reported."

EPA opened the second portion of the summit to press.

Later Tuesday, Wilcox said the AP was made aware ahead of time the event was at capacity, and was asked to leave, but the EPA also provided an overflow room.

"Last night, the Associated Press was told we were at capacity and a livestream would be available," Wilcox said. "The AP reporter showed up at EPA but refused to leave the building after being asked to do so. When we were made aware of the incident, we displaced stakeholders to the overflow room who flew to Washington for this meeting so that every member of the press could have a seat."

CBS News' Caitlin Conant contributed to this report.