Mike Heyworth, president of the Council for British Archaeology, was trudging home after a long, hot day in the office when he was startled to find fragments of Roman bone and pottery lying on a heap of soil at the end of his road.

The trench dug by a utilities company in York, which had sliced through an ancient cemetery, was on the corner of a residential street near the city's racecourse.

But it was also just across the road from a site that made headlines worldwide:, a pit under suburban back gardens where more than 80 skeletons of young gladiators – including one with bite marks from a lion, and decapitated skulls with the marks of hammer blows – were excavated.

The fragments of leg bone, and a jaw with teeth, that Heyworth happened upon may be a less sensational discovery. But he was astonished that nobody in the local authority had realised the sensitivity of the site – particularly in an area where Roman remains are often found close to the surface.

"Permission had been obtained from the council by the utility company to excavate the trench but apparently no condition was made to have an archaeologist present on site. When a known archaeological site is disturbed by any sort of development, it is vital that archaeologists can monitor the work and make a record of anything that is found," he said.

Heyworth says the incident shows up the "black holes" that are appearing in local authority archaeology services, with planners taking decisions without any specialist advice.

He notified both the police to inform them that human remains had been discovered and the local authority, and work has now been suspended while an archaeologist investigates the site.