  Context: The recent discovery of a group of trans-neptunian objects (TNOs) in
a narrow region of the orbital parameter space and with surfaces composed of
almost pure water ice, being 2003 EL61 its largest member, promises new and
interesting results about the formation and evolution of the trans-neptunian
belt (TNb) and the outer Solar System.
  Aims: The aim of this paper is to obtain information of the surface
properties of two members of this group ((24835) 1995 SM55, (120178) 2003 OP32)
and three potential members (2003 UZ117, (120347) 2004 SB60 and 2005 UQ513) and
to use that in order to confirm or reject their association.
  Methods: We obtained visible spectra of five TNOs using the 3.58m Telescopio
Nazionale Galileo at the ''Roque de los Muchachos Observatory'' (La Palma,
Spain)
  Results: The spectra of the five TNOs are featureless within the
uncertainties and with colors from slightly blue to red (-2<
S'<18%/0.1microns). No signatures of any absorption are found.
  Conclusions: We confirm the association of 1995 SM55 and 2003 OP32 with the
group of 2003 EL61 as their spectra are almost identical to that of 2003 EL61.
Only one of the three candidates, 2003 UZ117, can be considered as a possible
member of the EL61-group, as its visible spectrum is compatible with a spectrum
of a surface composed of almost pure water ice and no complex organics. The
other two, 2004 SB60 and 2005 UQ513 are red and must be considered as
interlopers.
