Firefighters answering an emergency call at a hospital found the doors locked.
Crews from Central Scotland Fire and Rescue Service were unable to access an area of Falkirk Community Hospital during the weekend callout.
Meanwhile, anxious staff, patients and relatives were left wondering if wards would be evacuated.
NHS officials are now updating access plans and reminding staff of evacuation procedures. They are also looking at how keys for locked areas can be provided quickly in an emergency situation.
The drama unfolded at the hospital on Sunday, July 22, around 2.45 p.m.
As relatives and friends arrived to visit patients, many of them elderly, the alarm began to sound.
Within six minutes, a crew from Larbert Fire Station and a crew of part-time firefighters responded to the call.
However, they found their way to the surgical assessment area blocked by locked doors as they tried to isolate the alarm.
Joe Andrews, watch manager operations with the fire and rescue service, said: “Members of the public had already evacuated some areas using the staircase but with the alarm continuing to sound, firefighters eventually stopped people going into wards.
“There was no sign of smoke and we weren’t going to force open expensive doors so asked for the keyholder to attend.
“However, they were at the Clackmannan site and it took around 30 minutes for them to get there, although this isn’t unusual with a facility of this type.”
He added that the crews then had problems isolating the problem and were eventually at the hospital for over 90 minutes, despite it being a false alarm.
One woman who was visiting an elderly relative said people were unhappy at the lack of information being provided.
She said: “It was a terrible situation. We were asked to leave but had no idea what was happening with the patients, who were two floors up and many of them have mobility problems.”
A spokeswoman for NHS Forth Valley confirmed firefighters had been called to the hospital but the incident was a false alarm.
She said: “As a result, there was no need to evacuate patients or visitors.
“However, in the event of a real fire detailed evacuation plans are in place. These include using the lifts to evacuate staff, patients and visitors under the direction and control of the fire service.
“We are currently working with the fire service to improve access across the site and are exploring the possibility of installing a control panel and key box which could be accessed by them on arrival.
“We are also working with staff to remind them of the fire and evacuation procedures currently in place.”