Medieval treasures could be buried beneath the site of Preston's £750m regeneration project, it has been claimed.
Archaeologists think there could be relics from the "medieval and post-medieval periods, and perhaps even earlier" under the 30-acre site.
Investigations are to start next month so that, should anything be found, it can be incorporated into the already delayed time schedule.
Council bosses have stressed that the work is routine for a planning application of this size.
Last year, a development was delayed when 30 graves, 12 of them containing virtually complete skeletons, were discovered off Marsh Lane.
Experts said the graves, less than a mile from the Tithebarn site, were the likely remnants of a medieval friary located in Preston from 1260 to 1539.
The Tithebarn developers will be asked to provide information on how their proposals for the flagship site could impact on any remains.
County archaeologist Peter Iles, employed by Lancashire County Council, said: "There may be further recording or excavation to be done.
"There may be areas we'd like to see preserved but we can't say that until the investigations are undertaken.
"It's not an archaeologist jumping in front of a bulldozer.
"We feel it needs to address the archaeology of the town – this is quite a normal procedure.
"Much of the town is fairly modern, and therefore when an opportunity comes up for these things to be looked at, it's only right and proper that it's investigated."
He said any delays to the project would "depend entirely on what is found and what they intend to do on that area of the site" but some remains may be buried deep enough to build over.
He said: "There's no reason to suspect it will cause significant delays to the development.
"They're doing this work early to make sure there are no unwelcome surprises."
Exploratory work will be carried out as part of other investigations needed before a planning application is submitted, such as ground conditions.
The Tithebarn project has already been beset with delays and the latest date for completion is 2014.
Town centre ward Respect councillor Michael Lavalette, said: "Obviously, if there are important artefacts under the Tithebarn area, I would hope that they suspend the regeneration.
"It could be about finding important parts of history and the past.
"They need to do proper investigations and find out what is there."
A spokesman for Preston Council confirmed work would start next month on digging boreholes but said the vast majority of the Tithebarn area was re-developed in the 1960s.
He said: "We'll listen to what the county archaeologist says, and if there's an area they want us to focus on we'll look at that."