HANSCOM AIR FORCE BASE (AP) — Normal operations resumed at an Air Force base that was partially evacuated early Thursday, when potentially explosive material was detected during a routine inspection of a delivery truck.

In a statement, the 66th Air Base Group said the truck had been cleared and personnel who had been ordered to leave Hanscom Air Force base earlier in the day were being allowed to return.

“However pallets from the truck, which contain potentially concerning residue, have been removed and will be taken to a specialized facility for testing,” the statement continued.

The truck was stopped at about 9 a.m. at one of the entrances to the base, which is about 20 miles west of Boston.

There was no indication from authorities what type of material might have caused the concern. Several buildings were evacuated, and state police set up a 1,500-foot perimeter around the truck. An exit leading to the base from another route was also closed.

Massachusetts State Police Sgt. Fran Leahy defended the partial base closure, saying an initial inspection of the truck detected the possible presence of explosives and a special canine unit also got a hit.

“Given the times we live in, we operate in an abundance of caution,” he told reporters, adding that there were no suspects or arrests and none expected.

State police bomb squad commander Sgt. William Qualls said the tests underway hopefully would determine the origin of where the trace amount of explosives residue that triggered the alarm.

“There was something there at some point in time,” Qualls said. He said the truck was delivering personal belongings to a new base member when it was stopped.

The truck is owned by Big Foot Moving & Storage. The company issued a statement expressing relief that the incident was resolved and saying “we take this matter very seriously.”

Hanscom Field, a civilian airport adjacent to the base, remained in operation throughout the incident, according to the Massachusetts Port Authority, which operates the commercial facility.

The Air Force base has been in existence since 1941 and has served as a major military research center.

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