PHILADELPHIA (CBS) – The recent heightened awareness of threats around the 10th anniversary of the September 11 attacks have caused Homeland Security to get involved in the investigation of a weekend incident in which four U-Haul trucks were stolen in Philadelphia. Three of the trucks were recovered Tuesday morning.

Philadelphia police and investigators from the U.S. Department of Homeland Security investigated two recovered U-Haul rental trucks, found in the Kingsessing section of the city in the early hours of Tuesday morning. The vehicles were within a block of each other near 54th and Chester.

Authorities say they were stolen from other locations in Philadelphia over the weekend.

The trucks were cordoned off. Homeland Security and the FBI were called in and the trucks were checked for explosives but authorities have given the all clear.

Captain Walt Smith, with Homeland Security, says this was taken seriously, especially with the timing of the thefts.

“These vehicles could possibly be used for that type of activity (terroristic) but we don’t believe there’s any terrorist nexus to these vehicles at all. They have been cleared by our bomb squad as well as our canine units. They will be towed for further investigation by the Philadelphia police department,” Captain Smith said.

Some homes near the scene were evacuated while the trucks were checked out  as a precaution. All of those who were evacuated have since returned.

Later Tuesday morning, a third truck was found in North Philadelphia.

Police are looking for a 2005 white Ford E350 with Oklahoma license plates that is still missing.

Reported by Jim Melwert, KYW Newsradio 1060 and Nicole Brewer, CBS 3