Thousands of runners complete route after race is cancelled because of lack of water, despite police attempts to stop them

The Sheffield half-marathon descended into chaos on Sunday as organisers officially cancelled it due to lack of adequate water supplies – but many competitors ran on, with no idea it had been called off.

Some 5,000 runners were gathered at the start line when organisers suddenly announced the race could not go ahead on safety grounds as expected water bowsers had not arrived.

But not all runners heard the announcement, and as defiant front runners decided to go anyway, others followed in the mistaken belief the race had officially started.

Police initially tried to set up road blocks to stop them, but swiftly decided it was safer to let them continue.

As news of the water shortage was broadcast, well-wishers lined the 13-mile route handing out water they had brought themselves.

Furious participants condemned the organisation as a shambles but praised the community spirit that led Sheffield's unofficial half-marathon to be dubbed "the people's race".

Insp Neil Mutch of South Yorkshire police told the BBC: "We attempted to convince runners not to carry on, but decided it was a lesser risk to let them run the race."

Runner Helen Moody, 36, from Sheffield, said the race had been delayed, and she heard some booing, but when others started running she set off with no idea it had been halted. "I've seen stories saying we all carried on regardless [of the cancellation] but most of us didn't know," she said. "The amazing part was that random people were just handing out water bottles. Costa Coffee were handing out little cups of water. There were people who had washed out litre cartons of milk and were handing those out – so it won't have damaged the reputation of Sheffield."

Rick Long, 47, from Sheffield, who also completed the race, said: "I only found out it was cancelled on the radio in the car on my way home."

"The start was a total fiasco," he said, adding there was no official information for the delay. "Then at about 9.50am the front runners set off. I was about 200 back and there was no police stopping people running. No one around me had any idea that it had been called off."

Throughout the city, families left their homes on hearing the news to hand out refreshments they had bought themselves. On Ecclesall Road local shops ran out of bottled water.

Daisy Cole, 26, whose cousin and uncle were among those scheduled to run, and who handed out eight bottles, said: "I think it is pretty shocking, really, and it looks bad for Sheffield."

Nichoela Lafferty, 44, planning to cheer on her husband, said he had texted her to say it was running late due to technical difficulties. "And then word of mouth went round that there was no water on the route.

"It's a bit of a farce really. People have been let down."

Emer Murphy, who also completed the run, later posted on the Guardian website: "To be honest most people weren't aware it had been cancelled," adding: "The people of Sheffield were amazing, handing out water and jelly babies."

Organisers later tweeted "Those who crossed the finish line with their race number will be timed and we'll be providing a list of all finishers and their times."

Margaret Lilley, chair of the race organisers, told the BBC: "The company we had asked to supply bowsers for the route did not arrive this morning." The race was cancelled on safety grounds, but, she said, "the runners decided they wanted to go on the run anyway". The roads were closed and volunteer marshals already in place, she said.

"It is embarrassing, yes, and we will be carrying out investigation into why the water we were expecting didn't arrive.

"We are sure that everybody has finished their run safely, and we want to thank everybody who did help at the last minute."

Nick Clegg, deputy prime minister and Sheffield Hallam MP, said: "Everyone deserves a full explanation of how this farcical situation was allowed to happen. Sheffield is an outstanding city of sport. The extraordinary scenes today shouldn't tarnish that reputation.

"The fact that runners who had carried on regardless were still well supplied with water thanks to spectators tells you everything you need to know about Sheffield people."

The BBC's Football Focus presenter, Dan Walker, who was watching the run, said of the city's good Samaritans: "It's good to see the people of Sheffield have turned out anyway. They're determined even if the organisers have slightly messed things up. It shows the spirit of the people of Sheffield."

Asked whether he'd ever heard of anything like this happening before, he responded: "Never."

"When you organise a half-marathon, you think what do we need? We need a course, we need some cordons and we need water. To not have one of those three, well you've left yourself open to a bit of criticism really," he added.

Of the police attempt to set up road blocks, he said: "It sounds like they turned it into a bit of a steeplechase."