Two boys who signed up to Pedal for Scotland after the death of their grandmother were left "devastated" after being knocked out of the race.

At least fifty cyclists were unable to finish the event after their tyres were punctured by metal tacks.

Others reported running over broken glass and police are investigating whether Sunday's race was sabotaged.

Dave Taylor, 38, said his sons Luke, eight, and Aaron, nine, joined the event to raise money for Lupus UK.

The disease claimed the life of Mr Taylor's mother Joyce, who died last year aged 66.

The trio were about two miles outside the village of Slamannan in Falkirk when Aaron suffered his first puncture after running over glass.

"We stopped and changed that because we had an inner tube with us and got going again," Mr Taylor said.

"We got about another 500 yards and got another puncture. At that point we were questioning our luck," he added.

"We walked into town with the bike and tried to get it repaired but the inner tube kept popping and we just couldn't continue. The boys were devastated."

The majority of cyclists who suffered punctures as a result of debris on the road on Sunday were hit in Whitecross, Falkirk, and Linlithgow, West Lothian.

Organiser Cycling Scotland said it risked causing serious harm to cyclists, although nobody was injured.

At least two other cyclists were knocked out of the race at Slamannan by broken glass, which appeared to have been spread out across the road.

Mr Taylor, from Glasgow, said the experience had been "heartbreaking" for his sons, who have raised £2500 for lupus research.

"It was quite a meaningful day for us, so the boys were really disappointed," he said.

"They really bought into the challenge and to be denied the opportunity to finish was particularly heartbreaking."