Several sub-domains on the website of the National Aeronautics and Space Administration are offline following an attack by hackers opposed to National Security Agency surveillance programs.

"Stop spy on us," said a message posted Monday to the pages of several NASA programs. "The Brazilian population do not support your attitude!"

The hack was first reported Tuesday by Internet news website Hack Read. According to that report, 14 sub-domains were initially affected.

"[A] Brazilian hacker group posted a political message on a NASA website," agency spokeswoman Beth Dickey told U.S. News. "NASA discovered the message within hours of its initial post and immediately started an investigation. The investigation is ongoing."

Earlier in September Guardian reporter Glenn Greenwald disclosed that, according to leaked NSA documents, the communications of Brazilian President Dilma Rousseff and state oil company Petrobras are monitored by the U.S. spy agency, infuriating many Brazilians.

Although the primary complaint motivating the hack appeared to be NSA surveillance, smaller text on the hacked web pages expressed opposition to potential U.S. air strikes against Syria's government.

The space news blog NASA Watch reported Wednesday the initial language was replaced by an offline message that said "Down For Maintenance."

Pages affected included the Kepler spacecraft's page, four moon-science pages, one belonging to the NASA Aeronautics Research Institute and NASA's events page.

As of Thursday morning, the page of NASA's Office of Planetary Protection, which aims to minimize biological contamination while exploring space, a page of the NASA Center for Astrobiology, and space history page moon fest remain offline.

A hacker group called "#BMPoC" claimed responsibility for the attack. Three individuals identified themselves as "Cyclone," "MMxM" and "UTOPI4." The same group attacked other NASA pages in April, Hack Read reported. The reason for that attack remains unclear.

Sensitive space agency information was not comprised, according to NASA.

"IT Security remains a critical function at NASA," Dickey said. "At no point were any sensitive, mission, or classified systems compromised."