'20/20' Anchor Elizabeth Vargas In Rehab for Alcohol Abuse

“20/20” co-anchor Elizabeth Vargas has been MIA for weeks ... and now we know why -- she's been in rehab for alcohol abuse.

Vargas checked into rehab a couple weeks ago -- according to the NY Daily News -- and will remain in treatment for a few weeks more. She'll return to "20/20" when she's released from the rehab facility.

Vargas released a statement saying she suffers from addiction, claiming, "I realized I was becoming increasingly dependent on alcohol. And I feel fortunate to have recognized it for the problem it was becoming."

She adds, "Like so many others, I will deal with this challenge one day at a time."