A 42-year-old man was last night being questioned by police in relation to an ongoing investigation into criminality linked to the east Tyrone New IRA.
He was detained in the Cookstown area yesterday.
PSNI Detective Inspector Martin Cush said the arrest was in "connection with the illegal disposal of tyres by east Tyrone New IRA and associated criminal enterprises for the purposes of terrorist funding".
"His arrest follows the arrest of two men aged 41 and 42 on Wednesday 5 August after officers conducted four searches and uncovered a substantial sum of cash concealed in a recycling bin and safe.
"The cash was seized for further examination and the two men later released following questioning.
"Where possible, we will continue to disrupt violent dissident republicans but need help from the public in tackling their criminal activities. They are reckless, manipulative and they exploit their own communities.
"Our objective is to keep people safe and protect them from these violent groups and any information we receive can increase our chances of success."
