London Underground passengers were trapped in a locked station for nearly 45 minutes during Monday's Tube strike.
About 20 people got off a train when the driver accidentally opened its doors at the shut Canada Water station in east London, at about 1700 BST.
Commuter Juliet Schenker, who had been trapped, accused Tube bosses of running "an unsafe service during the strike".
But Transport for London (TfL) said it "wasn't putting anyone's safety at risk".
London Underground's chief operating officer Howard Collins said: "We sent a supervisor to go down to get people back on the next train - about 15 to 20 people.
"Those people got back on but unfortunately we believe two people had tried to exit the station and spent some time to find their way out."
Passenger Ms Schenker, who found her way out through a fire exit, said: "I started thinking 'What if I was ill? What if there was a fire?' It was a build up of panic.
"TfL was running an unsafe service during the strike.
"I don't think that's acceptable."
But Mr Collins said the incident was because of "human error" and he could "only apologise".
He added that LU was "carrying out a full investigation" and would "learn lessons" from the incident.
The RMT and TSSA unions were on strike on Monday in the second in a series of walkouts over cuts to 800 ticket office jobs.
TfL claimed it was able to keep 75% of stations open and 40% of Tube trains running on the day.