An Al-Qaida affiliate has developed a new generation of liquid explosive that U.S. officials fear could be used in a future attack, ABC News reported Monday.

Two senior U.S. government sources who have been briefed on the terror threat that prompted the U.S. to close embassies across the Mideast and North Africa this week, told the network that clothes dipped in the liquid become explosive devices when dry.

One of the U.S. officials described the new generation explosive as "ingenious," while another said it would be undetectable under current security processes.

The liquid explosive is believed to be the brainchild of the Yemen-based affiliate Al-Qaida in the Arabian Peninsula (AQAP), the officials told ABC News. This affiliate is home to Ibrahim al-Asiri, a master bombmaker, who was on the 25 "most wanted terrorist" list published by the Yemeni government.

A number of U.S. embassies in the region were closed Sunday after the U.S. intercepted communications between the leadership of AQAP and Al-Qaida's remaining leadership in Pakistan, which suggested a major operation was underway, according to senior U.S. officials. The diplomatic posts are expected to remain closed this week.

The New York Times reported that the closure of the embassies was the result of intercepted electronic communications between Ayman al-Zawahri, who replaced Osama bin Laden as head of Al-Qaida, and Nasser al-Wuhayshi, the head of Yemen-based affiliate Al-Qaida in the Arabian Peninsula (AQAP).

U.S. sources said that while some type of message between Zawahri and AQAP was intercepted recently, there were also other streams of intelligence that contributed to the security alert, which was prompted by a threat from AQAP.