Work on the Aberdeen bypass has been shut down for four days while workers are given safety training.

Only the most critical work will be carried out on the Aberdeen Western Peripheral Route until Tuesday.

It follows the collapse of a 30ft-tall steel frame at the site earlier this week, which Transport Scotland said is unrelated.

But a construction union has accused the consortium of contractors running the project - Carillion, Galliford Try and Balfour Beatty - of covering up accidents.

A spokesman for Transport Scotland said: "We understand that an incident took place on site despite the contractor having robust health safety policies and procedures in place.

"We also understand that no-one was in the vicinity at the time of the incident. An investigation is currently underway and any lessons learned will be applied to future work.

"Some works will continue to take place this weekend. A safety stand-down, which has been planned for a number of weeks, will take place between Friday and Monday, which demonstrates the contractor's on-going commitment to health and safety.

"It is not unusual for this type of exercise to be held over consecutive days so that all workers can take part at the same time."

It is believed to be the third scheduled safety shut down at the site this year.

Steve Dillon, regional secretary of the Union of Construction, Allied Trades and Technicians (Ucatt), claimed standard industry safety protocols were being "flaunted" during the construction of the AWPR.

He said: "One of the major problems is that there is a safety committee but it not's being used in compliance with health and safety regulation.

"It was not informed of these events and therefore the committee is not carrying out its function properly - and the result is serious accidents."