Runners from our region have described how they avoided being caught up in the deadly explosions in Boston by a matter of minutes.
Some 347 of the 25,000 taking part in the race were British and several told of the aftermath of the two blasts.
Abi Griffiths, from Brighton, crossed the finishing line around 10 minutes before the "chaos".
The 34-year-old told Sky News she heard the explosion while collecting her bag.
"The ground shook and immediately people sort of looked around - it was just too loud to be something that wasn't serious," she said.
"People kind of didn't know what to do. Then all of a sudden it went into a state of chaos.
"Police were everywhere, we were being evacuated out of the area and it was really eerie.
"It was very, very scary and what should be a major celebration of the achievement of running 26.2 miles suddenly became a frightening scene."
She said police had swung into action quickly.
"This is just such an awful scene to have happened," Ms Griffiths continued. "It felt like it may have come from the inside of a shop.
"Suddenly you looked around and there was this cloud of smoke and then people went into gear. There were police everywhere."
Darren Foy, 40, from Southampton, his wife Sandra and their two children, missed the explosions by just half an hour after he finished the marathon in three and a half hours.
The chartered surveyor, who is chairman of the Lordshill Road Runners in Southampton and was competing in his fourth marathon, said: "There are reports here that the explosions came from a hotel at the finish line and I walked past there a few days ago to pick up my race number.
"It's such a soft target. There are hundreds of thousands spectators on the streets and 27,000 runners, so we got off lightly."
Chris Bird, chief executive of Sports Tours International, which organised for 51 people to go to the Boston Marathon - 40 runners and 11 non-runners - said all were accounted for.
"We spoke to every single one, the team back at the office, in the incident room, spoke to families and to runners that we could get hold of and our team on the ground in Boston spoke to everybody and checked them all into the hotel," he told BBC Breakfast.
"Thankfully everybody is safe."
Some runners travelling with his company completed the race, but most had been been pulled off the course to safety after the blasts took place, he said.
"They were pulled off the course and were really just pulled away from any area of danger or potential danger and needed then to make their own way back to their hotel," he said.
"Over 300 British people ran the Boston Marathon and the majority will have run for a cause either close to their hearts or close to colleagues or they will be raising money for some sort of good cause. So it means a lot to everybody and the emotions attached to it are really high.
"Something like this really focuses the mind on what is really important."