Three people were killed and more than 20 injured when scaffolding for a bridge collapsed over Johannesburg’s main motorway on Wednesday, sending the share price of construction group Murray & Roberts, the contractor behind the project, tumbling.

The company’s share price fell more than 7 percent in late trade to R11.15 after news of the tragedy broke.

“Murray & Roberts can confirm that this afternoon a support structure that was erected to enable the construction of a pedestrian bridge … collapsed,” the firm said in a statement.

“The exact cause of the incident is not known at this time. All of our incident-response procedures have been initiated, our support services have been mobilised and relevant authorities have been advised.”

Martin Lentsoane, the managing director of Lehumo Capital, a financial consultancy, said shares in the construction sector had been under pressure but the accident contributed to the sharp drop in Murray & Roberts stock.

“The news around the company would be negative after the accident and this contributed to the fall in the shares. There are questions on how the bridge was constructed, there could be lawsuits, regulators will be investigating – all these could be more bad news,” Lentsoane said.