Authorities expand downstream evacuation from potentially dangerous "quake lake"

MIANYANG, China (CNN) - Authorities are expanding evacuation plans in southwestern China as water piles up behind a dam created by an earthquake landslide, state-run media reported Friday.

An additional 40,000 people in Beichuan county have been ordered to leave at-risk areas downstream from the so-called quake lake, bringing the total to nearly 200,000.

Tangjiashan Lake didn't exist prior to this month's massive quake in Sichuan province, which sent a hillside crashing into the Jianjiang River.

Local officials are preparing for the worst - a possible catastrophic failure of the quake-created dam. Their plans call for a practice evacuation of 1.3 million people over the next four days.