Yemeni special forces launched an offensive Tuesday across two rugged provinces searching for an Al Qaeda bomb maker believed to have devised the concealed explosives that were intercepted in two packages last week before reaching the U.S., the Los Angeles Times reports.

The hunt for Ibrahim Asiri, a Saudi-born munitions expert, intensified in militant strongholds in Shabwa and Marib provinces. It is the third major operation against Al Qaeda in recent months but one that has taken on new urgency since a plot was uncovered to blow up airliners over the U.S.

Investigators allege that Asiri also provided the explosives in a 2009 suicide bombing carried out by his brother in a failed assassination attempt against the head of Saudi Arabia's intelligence agency. He is suspected of having designed the bomb hidden in the underwear of a Nigerian student in an attempt to bring down a U.S. airliner in December.

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