U.S. House leaders are seeking answers as to why hackers were able this week to deface nearly 50 websites belonging to the lower chambers’ members and committees.

In a letter Thursday, Speaker Nancy Pelosi, D-Calif., and Minority Leader John Boehner, R-Ohio, requested an “immediate and comprehensive” review of the incident by Daniel Beard, the House’s chief administrative officer.

Soon after President Obama delivered his State of the Union address on Wednesday night, the websites for Reps. Charles Gonzalez, D-Texas; Spencer Bachus, R-Ala.; and Brian Baird, D-Wash., were among those defaced with profane messages directed at the president. In addition, several committee sites were hit, including the Financial Services Committee, the Committee on Oversight and Government Reform, and the Committee on House Administration.

A group of hackers from Brazil, called the Red Eye Crew, have claimed responsibility for the cyberattacks. Robert Brady, chairman of the Committee on House Administration, which oversees the Beard’s office, said in a statement Thursday, that the intrusion “should be viewed as attacks on our system of government.”

The defacements prevented thousands of constituents from being able to communicate with their elected officials, Brady said.

“These efforts to prevent Americans from accessing their government will not be tolerated and transcend any political ideology or party affiliation,” Brady said. “I applaud Speaker Pelosi and Republican Leader Boehner for acting decisively in calling for immediate action.”

Pelosi and Boehner said in their joint letter that they appreciate recent efforts Beard and his team have taken to improve cybersecurity, including tightening firewalls and securing mobile devices from hackers.

“However, last night’s actions indicate that further review of security procedures are needed,” the letter stated.

The lawmakers also requested a security review of the third-party vendors used by the House. Specifically, the lawmakers questioned whether GovTrends, a Virginia company that managed the defaced websites, adhered to House security standards.

“While many members have expressed satisfaction with the vendor in question, this is the second time in a year websites hosted and supported by this vendor have been compromised,” Pelosi and Boehner said in the letter. 

A spokesperson at GovTrends did not respond to a request for comment.

Last August, 18 House sites managed by GovTrends were defaced, Jeff Ventura, a spokesman for Beard, told SCMagazineUS.com on Thursday.