Researchers at the Institute of Cancer Research have identified two genetic mutations that could triple a person's risk of developing bowel cancer.
A previous study found the first section of the human genome linked to bowel cancer.
Now, researchers have found another two mutations within that which could raise the overall risk two to three-fold.
The team said that they could cause a third of all cases - about 12,000 per year.
Previously, researchers found a part of the genome, which is responsible for causing Hereditary Mixed Polyposis Syndrome (HMPS) - a condition that significantly increases bowel cancer risk in Jews of Ashkenazi descent.
They then went back in an attempt to find the specific genes responsible for HMPS.
However, instead of finding genes specifically relevant to Ashkenazi Jews, they made a discovery with much wider implications.
They discovered that the HMPS region also had two faults, which are present in many more cases of bowel cancer in the general population.
Professor Ian Tomlinson, joint lead researcher at the Institute of Cancer Research said he was 'delighted' at the finding.
"Finding out that a region we thought was only relevant to bowel cancer risk in Ashkenazi Jews was also related to risk in the wider UK population is very important. This could help us understand how different variants of the same gene affect risk and how genes interact to increase overall risk," BBC News quoted Prof Tomlinson, as telling Nature.
Dr Lesley Walker, director of cancer information at Cancer Research UK, said that previously, researchers had focused on high risk genes - those which caused a particular cancer in many generations of the same family, often to devastating effect.
"Most of those high risk genes have now been discovered. So the emphasis has moved to genes which do carry a risk, but a lower one - genes which are much more common in the population," Dr Walker said.
On their own, the two newly found mutations present too small a risk to warrant the development of a screening test.
However, researchers hope that in the future it may be possible to develop a test for a combination of mutations like them, which on mass would more significantly increase the risk of bowel cancer.
The finding is the latest to emerge from an effort by Cancer Research UK to search the entire human genome for mutations linked to cancer. †
The study is published in the journal Nature Genetics.