Work on a HK$250 million extension at the King George V School in Kowloon has been halted after a steel pole fell 15 metres and speared a British teacher's BMW.
The three-metre pole crashed through a bamboo screen and pierced the windscreen and dashboard of the parked car at the English Schools Foundation (ESF) secondary school at 3.45pm on Monday.
The owner of the car, the head of physical education Charles Riding, declined to comment.
He is believed to have been inside the school at the time of the incident. Classes had finished but some pupils were still on site doing after-school activities.
Work on a new science block and performing arts centre, which began last July and is due to be completed next May, was suspended and an investigation launched into the incident, ESF spokeswoman Susanna Chiu said.
Extraordinary pictures of the damage to the car, caused by workmen accidentally dropping the pole, have circulated on Facebook and been shared among colleagues and the school's 1,500 pupils.
A staff member who asked not to be named said: 'It could have been disastrous and potentially fatal if a pupil or teacher had been in the area at the time. It happened shortly before the teacher would have gotten into his car to go home so he was incredibly lucky.
'The steel pole went straight through a bamboo screen that had been put there to stop anything falling on vehicles or people below. I hear the car is probably a write-off. I'm sure the teacher in question was shaken by what happened but he's a pretty cool character.'
The staff member added: 'This raises questions about whether the work is being rushed to get the new buildings completed as soon as possible, and whether it should be going on at all during term time.'
In written responses to questions, Chiu said: 'Yes, the incident was a risk to students and staff. ESF considers the health, safety and well-being of all staff, students and visitors to be our number one concern.'
She said that an investigation had been launched and measures would be taken to ensure a similar accident to not occur.
Asked if pupils or teachers might have passed the area where the incident took place, Chiu said the ESF had placed restrictions on the contractor and only allowed them to do construction work after students had left the campus 'to minimise the impact of construction on school activities and risks to students'.
'The incident took place after the end of the school day, when students had been dismissed from campus,' she said. 'Students and staff will not be passing this route when they leave school.'
A message to parents sent out by principal Ed Wickens at the end of the week said he expected work to resume in about one week, after increased safety measures were put in place - including additional netting and protective layers to catch falling objects from the worksite.