(CNN) -- The United States intercepted a shipment of packages a few weeks ago that was headed for Chicago, Illinois, and might have been a "dry run" by al Qaeda in Yemen, according to a U.S. official.
The official told CNN "there were some packages that attracted our attention several weeks ago that were interdicted and searched, but nothing other than books and literature were found in them." The official said there were concerns about the packages because they were shipped from Yemen and "there were connections to someone tied to the al Qaeda affiliate in Yemen." The story was first reported by ABC News.
The official said it is now believed the terrorists were "trying to learn something about the system," how packages move from overseas locations to the United States.
The official would not comment on where the packages were to be delivered in Chicago.
According to the official, the reason the United States mobilized so quickly last week when tipped off about possible bombs in cargo packages coming from Yemen was because of the previous incident.
"It's why we pulled out all of the stops," the official said.