Archaeologists from UCC are examining the remains of six people discovered on Tuesday by council workers excavating a site near Monaghan courthouse.
The team, led by Prof Margaret McCarthy, has yet to date the one undisturbed grave and five skulls, but it is believed they may be hundreds of years old.
The site is being developed by the town council to erect a bronze and sandstone sculpture to commemorate those who died in the Monaghan bombing of 1974.
Monaghan council engineer Mr Garret McMahon explained that although they could have waited to begin work on the monument next year, they began early because they were aware that the site might be of historical interest. He said the council had the archaeology team with them when the work began on Monday.
The team examined the remains, and the site has now been closed until a report is sent to the Department of Environment's heritage division.
Sources in the Clogher Historical Society based in Monaghan and the County Museum say the area where the find was made may have been a burial ground as far back as the 1600s.
The site where the present courthouse was built in 1829 was also the scene of public executions in the 1700s, when a jail was situated there.
The nearby St Patrick's Church of Ireland was also built around 1830, but was preceded by a church on the same spot by up to two centuries. This may also have a burial ground.