Two young men have been questioned by Milford gardaí in relation to a substantial amount of damage carried out to Lackagh Bridge, between Creeslough and Carrigart, recently.
A spokesman for Milford garda said they were following a definite line of enquiry and have interviewed two local youths in relation to the incident.
It is understood a JCB digger was used to destroy a large section of the iconic bridge.
They were released without charge and a file is now being prepared for the Director of Public Prosecution.
It is believed the machinery used was captured on CCTV earlier in the evening. The damage occurred just over a week ago on Friday November 26.
As well as a six metre stretch of the bridges protecting wall being knocked onto the banks of the Lackagh River, a number of public signs were also destroyed in the vandalism attack.
The damage is estimated to cost in the region of 10,000 euro,
The men were also questioned in relation to a quantity of gravel belonging to Donegal County Council that was taken near the scene of the vandalism.
The damaged area has been cordoned off and the bridge still remains in use by local traffic.
The famous bridge was built in 1750 at a cost of 207.16.0 and was renovated by Donegal County Council in the 1970's.
It has featured in many famous Irish postcards and is a popular area with tourists and anglers visiting nearby Doe Castle.