We study the cosmological evolution on a brane with induced gravity within a bulk with arbitrary matter content .
We consider a Friedmann-Robertson-Walker brane , invariantly characterized by a six-dimensional group of isometries .
We derive the effective Friedmann and Raychaudhuri equations .
We show that the Hubble expansion rate on the brane depends on the covariantly defined integrated mass in the bulk , which determines the energy density of the generalized dark radiation .
The Friedmann equation has two branches , distinguished by the two possible values of the parameter \epsilon = \pm 1 .
The branch with \epsilon = 1 is characterized by an effective cosmological constant and accelerated expansion for low energy densities .
Another remarkable feature is that the contribution from the generalized dark radiation appears with a negative sign .
As a result , the presence of the bulk corresponds to an effective negative energy density on the brane , without violation of the weak energy condition .
The transition from a period of domination of the matter energy density by non-relativistic brane matter to domination by the generalized dark radiation corresponds to a crossing of the phantom divide w = -1 .