Central Scotland Police uncovered a total of nine buses - which had been carrying schoolchildren - with mechanical defects so serious they had to be put off the road immediately.
Multiple road safety breaches were discovered at Blair Drummond Safari Park, near Stirling, during a five-day operation carried out by officers of the road policing unit and members of the Vehicle and Operator Services Agency (VOSA) last week.
Sergeant Bob Murphy, of the collision prevention unit, said: “The buses were checked while pupils were inside the safari park and those with the serious defects were immediately taken off the road.
“The operators then had to find an alternative buses to collect the pupils once their visit was over.”
One of the most serious defects was an emergency door which could not be secured shut.
Sergeant Murphy said: “The door was basically filling the hole. If somebody had leaned against it they could have fallen out and the consequences do not bear thinking about.
“Bus companies are given the responsibility of safely taking pupils to and from school and on school outings. It is extremely worrying that nine buses were so defective they had to be removed from the road with immediate effect.
“We want to reassure parents that we will do everything we can, along with VOSA, to make sure their children are travelling on buses that are completely roadworthy. We will continue to address this.”
Faulty brakes, a faulty exhaust, oil leaks and a broken seat belt were among the other defects discovered, while 15 drivers were found to be working in excess of their hours or unable to prove the hours they had worked and were not allowed to resume driving until they had sufficient rest.