More than 420,000 houses collapsed in southwest China after two powerful aftershocks hit the region – already devastated by the country’s deadliest earthquake in 32 years, state-run Xinhua News Agency said.

A magnitude-5.7 quake hit at 4:37 p.m. today in the region, the U.S. Geological Survey said on its Web site. A 5.2-magnitude aftershock hit about half an hour earlier, USGS said.

A 6-magnitude quake in the area on May 25 left at least 8 people dead. The Aftershocks are disrupting relief work and bringing more rubble down from mountains.