 -- Authorities called in a bomb squad to Hanscom Air Force Base in Massachusetts after discovering potentially explosive material inside a moving truck there Thursday morning.

Around 9:45 a.m. ET, security at the base in Bedford notified police of a "suspicious truck" that had been stopped at the gate for a routine vehicle inspection. An assessment of the truck and its cargo revealed there may be "potentially hazardous material," according to the Massachusetts State Police.

A police bomb squad and air wing were deployed to the scene. An area around the gate where the truck was stopped was evacuated as a safety precaution. A perimeter extending 1,500 feet from the truck in all directions has been set up, police said.

An exit from Route 2A, a major roadway leading to the base, is closed while authorities investigate. Police are asking news helicopters to refrain from flying overhead in the meantime.