The investigation was ordered by the Federal Aviation Administration after questions from the Seattle Times, the newspaper reported.
The mechanics' complaint was made earlier this year because what they allegedly found was the same problem that led to the fatal crash of Alaska Flight 261 six years ago, the newspaper said.
Additional questions were raised after a second jackscrew incident last week, the report said. The jackscrew in the tail section is part of the plane's maneuverability system.
"We will interview all of the people involved," said FAA spokeswoman Laura Brown.
Alaska disputed the three mechanics' original complaint. The airline said the jackscrew had been lubricated during its last previous inspection.