LEDs aren't coherent light sources (lasers). Look at the data sheet for any of them and you'll see a "peak emission" wavelength as well as a range of wavelengths that may be emitted and often a graph showing a spectral curve indicating the amount of energy emitted at wavelengths on each side of the peak.
The term "ultraviolet" as used in marketing literature somewhat loosely describes a range of wavelengths, some of which are partially visible as with the example above involving infrared emitters. For example, Lumex offers six different wavelength options under the heading ranging from 355nm to 415nm. The longer of these will obviously have a significant visible component.