A 5.8-magnitude quake hit Puerto Rico before dawn Monday, unleashing small landslides, causing power outages and severely cracking some homes. It was one of the strongest quakes yet to hit the U.S. territory that has been shaking for the past week. There were no immediate reports of casualties. Another quake measured at magnitude 5.1 struck later Monday, at 10:51 a.m. (1451 GMT), shaking power lines and frightening residents of southern Puerto Rico who had been waiting outside their homes due to fears the buildings were damaged and unstable. The first quake struck at 6:32 a.m. (1032 GMT) just south of the island.