Bullet proof tests?

Is it possible that positive test results could be due to the effect of some gas (diesel fumes) other than radon? I have installed a sub-slab vacuum system in my home. The material removed from beneath the slab smells like diesel fuel. The exhaust from the system smells like diesel fuel. Is it possible that the excavator spilled or disposed of diesel fuel or used oil in the basement excavation and the fumes are causing a false positive radon test? Any opinions?