WASHINGTON — The Environmental Protection Agency barred The Associated Press and CNN from a national summit on harmful water contaminants on Tuesday — and guards forcibly shoved a female reporter out of the building.

The EPA blocked the media organizations, along with the environmental-focused E&E News, from attending the meeting in Washington, convened by EPA chief Scott Pruitt.

The @EPA told @AP, @CNN they weren't invited to @AdministratorPruitt's #PFAS summit. EPA guards grabbed AP reporter by shoulders, shoved reporter out of building when she asked to talk to agency public-affairs person about covering meeting https://t.co/9g1BZsG8cy — Ellen Knickmeyer (@KnickmeyerEllen) May 22, 2018

Guards barred an AP reporter from passing through a security checkpoint inside the building.

When the reporter, Ellen Knickmeyer, asked to speak to an EPA public-affairs person, the security guards grabbed the reporter by the shoulders and shoved her forcibly out of the EPA building. She said she was not injured and was later permitted to attend the meeting.

"The Environmental Protection Agency's selective barring of news organizations, including the AP, from covering today's meeting is alarming and a direct threat to the public's right to know about what is happening inside their government," said AP Executive Editor Sally Buzbee.

"It is particularly distressing that any journalist trying to cover an event in the public interest would be forcibly removed," Buzbee added.

CNN said in a statement that its reporter also was turned away from covering the event "after multiple attempts to attend."

"We understand the importance of an open and free press and we hope the EPA does, too," CNN said, according to the AP.

EPA spokesman Jahan Wilcox told the barred organizations they were not invited and there was no space for them, but gave no indication of why they specifically were barred.

"This was simply an issue of the room reaching capacity, which reporters were aware of prior to the event," Wilcox told NBC News. "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."

The reporter threatened "negative coverage" if she couldn't get in, Wilcox alleged.

Some media that had been permitted to attend said that there appeared to be a handful of open seats for the press in the room despite claims that there was no room left.

A reporter for E&E News tweeted about being shut out by the EPA.

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

Amid criticism for barring the media outlets, Wilcox announced later that the afternoon session of the meeting would be open to all press.

Following that decision, the AP said, "We are pleased that the EPA has reconsidered its decision and will now allow AP to attend the remainder of today's meeting. The AP looks forward to informing the public of the important discussions at the water contaminants summit this afternoon."

Pruitt spoke Tuesday as he opened a hearing on the contaminants, known as perfluoroalkyl and polyfluoroalkyl. The chemicals were used in items like nonstick coating and firefighting foam and have contaminated some water systems nationwide. The compounds are linked to developmental defects and other health problems.

Pruitt has faced criticism in recent weeks over emails showing the EPA sought to intervene in a critical study on the contaminants.

Convening Tuesday's session, Pruitt is pledging to work on establishing a maximum allowable level for the chemicals in drinking water.

Representatives of states, tribes, the chemical industry, environmental groups and others attended the session.