Extension of the human senses means not just the detection of changes by an artificial system, but also how that artificial sensory system can provide information about that to the human user. Warning signals serve the facilitation of detection of visual objects. We investigated how warning signals and signaled objects integrate into multimodal objects revealed by early evoked brain potentials. We asked whether locus of attention and stimulus intensity modulates this effect. 15 participants performed a driving and a redundant target paradigm task while EEG was recorded from scalp electrodes. We presented audio/visual/bimodal stimuli either with low or with middle intensity. We found that non-attended low intensity multisensory changes caused difference in attentional processing as early as 88 msec, on the other hand attended middle intensity multisensory stimuli led to an enhancement of an early visual event related potential component, namely the C1. These results suggest that attention and stimulus intensity interact in multisensory perception. Our results raise attention to how warning signals and signaled objects integrate. Consequently a warning system that is capable of providing simultaneous and spatially consequent signals is proposed.