"U.S. citizens are strongly encouraged to maintain a high level of vigilance," the agency said on its website.
The FBI said Ayman al-Zawahri and Osama bin Laden coordinated the 9/11 attacks.
Mohammad Ahmad al-Qahtani was flown back to Saudi Arabia, to a treatment facility.
Boston Marathon bomber Dzhokhar Tsarnaev's $1,400 COVID-19 stimulus payment can be used to help pay the millions of dollars he is ordered to pay his victims, a judge has ruled.
The Justice Department is preparing to announce charges against two men from Britain who joined the Islamic State and were part of a cell that beheaded Western hostages in Syria.