When a charged particle moves through a particular region it is not deflected. From ths, can it be inferred that no magnetic field is present in that region ?

Explanation

We know, that when a charge q passes through a magnetic field B with a velocity v, the force acting on that charged particle, `vecF=q(vecb xx vecB)`
The cross product `(vecv xx vecb)` signifies that `vecF=0` when `vecv||vecB`. So, if the charged particle moves along or opposite to the direction of magnetic field, no force acts on it. Hence when charged particle moves without suffering any deflection, it cannot be inferred definitely that no magnetic field is present there.