Comment on "Gravitational collapse of cylindrical shells made of counterrotating particles''

The gravitational collapse of cylindrical shells made of counterrotating particles was considered in a recent article by Pereira and Wang [Phys. Rev. D 62, 124001 (2000)]. Although the general formalism derived in that paper is correct, the derivation of the equations for a particular application contains several errors and, therefore the rest of the analysis based on those equations requires revision. In this Comment we give the correct equations, and a brief analysis of the solutions. Two families of exact solutions are also derived and analyzed.