A three-year Health and Safety Executive investigation into a crane collapse that killed three men has concluded there was “no conclusive explanation” for the incident.

An extensive investigation involving the HSE, the Metropolitan Police and other experts has failed to establish a direct cause of the collapse of a tower crane at Canary Wharf in May 2000.

The HSE says it will take no enforcement action in relation to the accident on the HSBC site in Canada Square. Rosi Edwards, HSE acting chief inspector of construction, said: “While we have been unable to prove how or why this tragic incident occurred, the comprehensive investigation has identified a number of actions that the industry needs to take to avoid the risk of further incidents.”

In a statement the HSE said there was insufficient evidence for any enforcement action and added that it was not in the public interest to bring a criminal prosecution in relation to technical breaches of health and safety legislation that were not linked to the collapse of the crane and the three deaths. However, the HSE acknowledged that the decision could disappoint the families of those who died.

Michael Whittard, 39, Martin Burgess, 31, and Peter Clarke, 33, fell more than 120 m when the Wolff 320 BF tower crane overturned.

They were part of a team using a large “climbing frame”, incorporating a hydraulic lifting device, to raise the height of the tower crane when the accident happened.

The HSE said it believed work by the British Standards Committee and other regulatory organisations would lead to safer climbing operations.

It urged firms to take a series of measures, including fitting the crane with an anemometer to check wind speed, before climbing.