Children described how they saw two men fall to their deaths from the jib of a giant crane as they looked out of classroom windows.

They gasped in horror as they watched the two crane workers fall more than 100ft to the ground on the building site in the grounds of Durrington High School, The Boulevard, just outside Worthing.

Some were counselled for shock after witnessing the men falling after the crane collided with another yesterday.

The investigation into the incident continued today and a decision will be made during the weekend as to how the remaining crane can be dismantled safely.

The two experienced workers were dismantling two giant cranes which have been part of the Worthing skyline since July.

Another construction worker, in his 50s, suffered serious head injuries and remains in a stable condition at Worthing Hospital.

As the large green crane came crashing down yesterday morning, lifting wires became entangled with a 100ft red crane, bending that crane's jib in half. It was left hanging precariously over a new school building.

The accident sparked a major alert. Police closed roads next to the school and West Sussex firefighters stood by while health and safety officials started their investigations.

The two crane workers worked for the nationwide construction company Willmott Dixon, based in Letchworth Garden City, Hertfordshire. Police said they did not live in Sussex and had been employed to dismantle the cranes.

The company said it would make no comment about the accident but was co-operating fully with officials from the Health and Safety Executive.

Police said they would name the two construction workers, who died instantly, once relatives had been informed.

Pupils saw the drama unfold as they sat in lessons.

The construction site for the new £11 million Highdown School for children with special needs is 150 yards from the main Durrington High School buildings.

Senior staff visited all classrooms, telling pupils to keep calm and stay in their rooms until it was safe to leave the site. The pupils were sent home at lunchtime.

Ryan Fleming, 16, who was in the middle of a science lesson, said: "Someone suddenly said, Look something's happening to the crane'. I saw the wires tangling then the red crane bend in half, catch the green crane and send it crashing on to the new school buildings. As the green crane fell I saw a man fall to the ground waving his arms. We were all in shock.Then the fire and ambulance services arrived."

Adam Reed, 15, who was also in a lesson in the science block, said: "Someone looked out of the window and said, Look the crane is coming down.' We saw someone jump from the crane.

"We just could not concentrate after that."

West Worthing MP Peter Bottomley, who visited the scene, said: "It is a tragedy for the families of the construction workers and I am confident the Health and Safety Executive will conduct a full and fair inquiry."

The accident could have been much worse as the crane toppled while workers were on tea break and there was nobody working on buildings where the crane fell.

Worthing Police commander Jason Taylor said: "There was no danger to the school children but we had to ensure they were safely inside the school while the situation was assessed."