The infection leads to massive stem bleeding and has been dubbed "acute oak decline" by Forestry Commission scientists.
Dr Sandra Denman, a senior forest pathologist with the commission's Forest Research, said experts first thought the trees were stricken with sudden oak death.
"However, our tests have confirmed this is not the case. Tests indicate bacteria from three different groups are associated with the bleeding areas.
"But we need to do a lot more work to identify the particular species of the bacteria. Research of this kind is very difficult and takes many months, even years."
The condition was first spotted in Booth Wood in Loughborough, Leicestershire, six years ago when a couple of trees were found to have tell-tale symptoms.
Last year more than 200 trees were blighted and oaks in the outer areas of the wood were discovered with the same bleeding cankers and rapid deterioration in health.
Experts took root samples, soil, bark and wood from diseased trees to determine if the problem was cause by either soil-borne or root-rotting organisms.