I am not sure what causes it but one really wierd thing I have seen more than once is that my non contact voltage testers when used in old houses with knob and tube or old two wire romex sometimes will give me continuous voltage readings off the wooden walls, door jambs or whatever else in the house I touch them near. I figure that this must be inductance or capacitence, from how they used to wire three ways with two wire cables for travellers and the hots and neutrals for same on different circuits. Anybody else ever see this or know why?
