  The class of accelerated reference frames has been studied, on the basis of
Fermi-Walker coordinates. The infinitesimal transformations connecting two of
these frames has been obtained, and also their commutation relations. The
outcome is an infinite dimensional extension of the Poincar\'e algebra.
Although this extension turns out to be Abelian, and hence trivial, it is
noteworthy that, contrarily to what happens with Lorentz boosts, acceleration
boost generators commute with each other and with translation generators.
