We present a high statistics analysis of the pure gauge compact U(1) lattice theory using the world-sheet or Lagrangian loop representation. We present a simulation method that deals directly with (gauge invariant) integer variables on plaquettes. The lattice action used is equivalent to the Villain form. We performed a finite size analysis of several magnitudes: the specific heat maximum, the Lee-Yang zeroes of the partition function, the latent heat and the interfacial free energy. All measured magnitudes and critical exponents are compatible with the presence of a weak first-order phase transition.