After initially closing American embassies and consulates across the Middle East and Africa this weekend in response to an unspecified terrorist threat, the State Department has said most of these facilities will remain closed for another week, through Saturday, August 10. The State Department currently has also issued a month-long worldwide travel advisory for U.S. citizens. Two embassies did re-open on Monday, in Afghanistan and Iraq, both postings that are heavily fortified, while State announced that four East African embassies that had been open will be closing for the next week.

Over the weekend, several lawmakers cautioned that the “chatter” was among the most serious threat since 9/11. House Homeland Security chairman Michael McCaul called it one of the “most specific and credible threats” he’s seen; Senator Saxby Chambliss, vice chairman of the Senate Select Committee on Intelligence, echoed McCaul, saying it was ”most serious threat that I’ve seen in the last several years.”

Lawmakers have not provided details on the nature of the potential threats, but CBS News reports the threat may be coming from Yemen, where the local al-Qaeda branch is among the most dangerous in the region; Britain, for example, closed its embassy in Sana’a as well and urged its citizens to leave the country.