The LIGO and Virgo detectors have observed several gravitational waves from mergers of compact binary objects, mostly binary black holes. These discoveries have allowed to start characterizing the astrophysical population of binary black holes, e.g. the distribution of masses and spins, which carry information about their origin. Still, these efforts are currently limited by the relatively small number of detections. Recently, we developed an independent pipeline to analyze public LIGO data and identified seven new binary black hole mergers, roughly doubling the sample of these systems. In this talk I will outline the main stages of the pipeline and describe the constraints we obtain on the properties of binary black holes.