ABC News correspondent Bob Woodruff has obtained a letter that an oil rig worker in Vietnam wrote to his employer claiming he saw Malaysia Airlines flight 370 intact and "burning at high altitude."

Woodruff tweeted an image of the letter:

Oil rig worker claims in employer confirmed letter-he saw the plane go down. Vietnamese say they found nothing @ABC pic.twitter.com/k8y02se9aZ — Bob Woodruff (@BobWoodruff) March 12, 2014

Woodruff warned in a separate tweet that the worker's claims are not confirmed and in fact could be a hoax: