Burning of superconducting thin film bridges by transport currents (up to  3×10⁷ A/cm²) is investigated by magneto-optical imaging of magnetic field distribution and low-temperature scanning electron microscopy providing Tc-maps. It is shown that  the destruction  is preceded by significant penetration of magnetic field inside a weak-pinning region. In relatively low-quality bridges one usually finds from magneto-optics the incipient burning  region.We show that in high-quality bridges it is the combination of the two techniques that allows to predict the place of burning.