(WSB Radio) -- MARTA says it will do a full investigation Monday into it's escalator at the Lennox square station that was shut down after it started accelerating Thursday night.

MARTA officials still haven't determined what caused the problem that forced passengers to jump off the escalator as they were leaving the lighting of the Great Tree at Lenox Square Mall.

"The escalator will remain out of service," spokesman Lyle Harris told WSB Radio. "We are going to keep it down until we can figure out what went wrong and get it fixed."

A witness told WSB Radio there was 'total pandemonium when the escalator malfunctioned Thanksgiving night.

Harris said Friday it was unclear if this escalator had any problems before Thursday night. He said MARTA has increased its safety reviews of escalator because of past problems.

In January, MARTA shut down 100 of its 149 escalators because of safety concerns.

The agency took the escalators out of service after learning a mechanic working for MARTA's maintenance contractor had bypassed a safety circuit on an escalator at the Dunwoody station. MARTA determined that the same mechanic had worked on or inspected scores of the machines.

A few are still out of service at the Five Points and Lindberg stations.

The problems started as much as eight years ago when an escalator at the Civic Center station went into a free fall in 2002.

In July of 2003, there was a problem with a down escalator at the Peachtree Center station, which drops 75 vertical feet. Witnesses reported the escalator sped up, slowed and then careened forward as screaming riders struggled to stay afoot.

On New Year's Eve 2007, the escalators at the Five Points MARTA station went into a free fall, injuring 11 people. MARTA said the braking system and a weak motor allowed the escalators to speed out of control.

Records showed that one of those three escalators was reported as going into a "free fall" six weeks earlier, on Nov. 17, 2007.

(Information from the AJC was used in this report).