Miranda Leitsinger of msnbc.com reports: Millions of people living along the Mekong River face a crisis that could destroy their lifeline and kill off whole species of fish: construction of a dam — the first of 11 proposed in the waterway's lower basin — in Laos.

Conservationists warn that the dam could significantly reduce the critical fish stock in the Mekong, the world's most productive inland fishery.

Laos deferred a decision on the hydropower dam Tuesday in the face of strong opposition from neighboring countries including its closest ally, Vietnam. But any decision could be a moot point, as a Thai newspaper reported Sunday that work on the project apparently began months ago despite questions and opposition from conservationists and Laos's downriver neighbors, Vietnam and Cambodia.

Read the full story and view our slideshow: The teeming Mekong.