// Workers had a "lucky escape" today as a 50-tonne steel roof rafter collapsed.
The accident sparked fears of further delays to the stadium as engineers tried to discover what went wrong.
Workmen were evacuated and sent home for the day following the incident at about 8.30am.
Multiplex managing director Martin Tidd described the incident as "minor" and said he hoped workers would be back on site tomorrow.
Engineers were assessing the situation but Mr Tidd said the roof structure had not been affected.
Early indications suggested that the roof rafter in the north west of the stadium had moved 20 inches.
Workers, including steel erectors, were "relatively close" to the incident.
"An investigation is under way and we are looking for a solution this afternoon. The indications are that it is not a design fault," he told a news conference.
The rafter involved in the incident was supported by temporary steel connections, said Mr Tidd, adding that nothing such as this had ever happened before at the site.
He denied that safety was being sacrificed to complete the project, and said one other beam similar to the once involved in the incident was now being checked.
Engineers said rafter No 24 on the north roof collapsed without warning, falling about one metre, as several workmen were working on it.
One engineer who witnessed the accident said: "I heard a really loud bang and looked round and saw the lads running away. //