U.S. congressional Republicans furious about being left out of the Donald Trump impeachment process stormed a closed-door witness deposition Wednesday and refused to leave, escalating a showdown over the investigation of the president.

More than two dozen lawmakers barged into a secure U.S. Capitol meeting room known as a SCIF, delaying the testimony of a Pentagon official, the latest witness in Democrats’ investigation of possible abuse of power by Trump over his pressure campaign against Ukraine.

It is a violation of U.S. House rules to access SCIFs — secure facilities designed to prevent electronic eavesdropping — without permission, and concerns were raised that lawmakers were committing serious security breaches by striding in with their mobile phones.

Some of the Republican encroachers apparently began tweeting from within the SCIF.

“BREAKING: I led over 30 of my colleagues into the SCIF where (House Intelligence Committee chairman) Adam Schiff is holding secret impeachment depositions. Still inside — more details to come,” tweeted rebel leader congressman Matt Gaetz, a fierce Trump defender.

A follow-up tweet suggested Gaetz was aware of the sensitivities of devices in the SCIF: “**Tweet from Staff**,” it read.

The incident caused Schiff to contact the House sergeant at arms about how to proceed, a Democratic lawmaker who watched the scene told The Washington Post.

The move, which Democrats branded a “stunt,” delayed the deposition of Laura Cooper, a deputy assistant secretary of defense responsible for Ukraine policy.

All members of the three House committees conducting the investigation, Democrats and Republicans alike, are permitted to attend the depositions and question witnesses

Congressman Alex Mooney, who stormed the SCIF with Gaetz, said in an audio recording posted online that Schiff “saw us, took the witness and walked out of the room, because they refused to have a hearing in a transparent way.”

Republicans opposed to impeachment appear to have settled on a new strategy to fight back: attacking the process itself, claiming it is invalid because the House has not taken a floor vote to launch an impeachment inquiry, and that it lacks transparency.

The Republican protest came two days after Trump urged his party to “get tougher and fight” against the investigation.

House Democrat Stephen Lynch said Republicans were seeking to “disrupt” the hearing to focus on the process rather than the substance of witness testimony.

They “wanted to exercise a right that doesn’t exist,” Lynch told CNN.