AMATRICE, Italy – Strong aftershocks damaged two key access roads into quake-struck Amatrice on Friday, threatening to isolate the tiny hilltop town as hopes dimmed that firefighters would find any more survivors from the earthquake that killed at least 267 people. Some crumbled buildings in Amatrice cracked even further after the biggest aftershock of Friday morning struck at 6:28 a.m., one of more than 1,000 that have hit the area since Wednesday’s quake. The U.S. Geological Service said it had a magnitude of 4.7, while the Italian geophysics institute measured it at 4.8. The shaking ground also damaged a key access bridge to Amatrice, forcing emergency crews to close it.