  Considering Chern-Simons like gravity theories in three dimensions as first
order systems, we analyze the Hamiltonian structure of three theories
Topological massive gravity, New massive gravity, and Zwei-Dreibein Gravity.We
show that these systems demonstrate a new feature of the constrained systems in
which a new kind of constraints emerge due to factorization of determinant of
the matrix of Poisson brackets of constraints. We find the desired number of
degrees of freedom as well as the generating functional of local Lorentz
transformations and diffeomorphism through canonical structure of the system.
We also compare the Hamiltonian structure of linearized version of the
considered models with the original ones.
