SAN FRANCISCO (KCBS)— A Muni train loaded with passengers pulled away from a station without the driver Wednesday morning.

The incident happened around 10:15 on the KT Ingleside Third Street train when the driver of the outbound train stepped out to fix a door and may have forgotten to set the emergency brake.

READ MORE: UPDATE: Judge Denies Bail for Los Gatos Mom Accused of Hosting Drunken Teen Sex Parties

Once the door was closed, Muni’s automatic control system thought that everything was in order and remotely activated the train to get it to the next station.

A rider brought the train to a halt in the tunnel between the Castro and Forest Hill stations by activating the emergency brake. No one was injured.

About 30 passengers were on the train as it traveled about a quarter-mile toward the Forest Hill station before someone pulled an emergency lever on board, causing the vehicle to come to a stop, according to John Haley, the agency’s director of transit.

He said that pulling the emergency lever was “an understandable reaction” from passengers, who did not know that the train could operate on automatic controls without an operator on board.

READ MORE: Oakland Accepting Applications For 2nd Phase Of Guaranteed Income Pilot Program

Haley said investigators will look into whether the operator pressed a red mushroom-shaped emergency brake button on the train before getting off to check on the door.

He said pressing that button before leaving the train is standard Muni procedure, and that if it had been pressed, “the train couldn’t have moved.”

The driver has been placed on non-driving status pending further investigation into the incident, Haley said.

The train was moved to the Forest Hill station then taken out of service so crews could check whether there were any problems with it, he said.

No one was injured in the incident, and Haley credited the passengers for staying on the train while it was stopped in the tunnel between the stations.

“It was a major help in terms of protecting their own safety,” he said. “It would be much more problematic if people had gotten out.”

MORE NEWS: Jefferson Award Winner Helps Keep Thousands Of East Bay Seniors Fed

(Copyright 2013 by CBS San Francisco. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)