BAGHDAD (AP) – A bomb rocked Iraq’s parliament building in the heavily fortified Green Zone Thursday, killing at least two lawmakers in a stunning security breach in the third month of an American-Iraqi crackdown on violence in the capital, officials said.

At least four other people were wounded in the blast, which shook a cafeteria while several lawmakers were eating lunch, initial media reports said.

Mohammed Awad, a member of the Sunni National Dialogue Front, was killed in the blast, said Saleh al-Mutlaq, the leader of the party, which holds 11 seats in Iraq’s legislature. Another female Sunni lawmaker from the same list was wounded, he said.

A security official at the parliament building said a second lawmaker, a Shiite member, also was killed. He spoke on condition of anonymity because he was not authorized to speak to the media.

Apparently concerned that an attack might take place, security officials at the parliament were using sniffer dogs earlier Thursday as people entered the building – a rare precaution.

A spokesman for the American Embassy in Baghdad, which is also in the Green Zone, said no Americans were injured in the blast.

“We are aware of reports of an explosion in the Green Zone. We are investigating the nature and source of the explosion,” spokesman Lou Fintor said. “No Embassy employees or U.S. citizens were affected.”