RAIL bosses have confirmed a fault in a heavily-used freight and passenger line in the North-East.

Residents on Teesside raised the alarm after spotting a gap in the ballast between rails running behind houses at Eaglescliffe.

They say that the track appears to "bounce" under the wheels of chemical and steel-hauling trains.

Railtrack says in a letter: "Track engineers have been to the location and identified that remedial work is required."

In the letter, to ward councillor John Fletcher, Railtrack representative Denise Thompson says the required remedial work will be included in "a routine maintenance programme", and assures him that safety is the company's first priority.

Railtrack said at the weekend it knew of no imminent work on the line, but residents claim engineers for Jarvis Facilities - the company carrying out line repairs at Hatfield - were working on the line last week.

The track where the engineers were working lies just above a 43-arch Victorian viaduct, which towers 100ft above Yarm.

There were two derailments within days in 1997.

Car windscreens and a garden conservatory were shattered and roof tiles dislodged as rocks and the inspection chamber lid were thrown off the bridge by a train in the second of the derailments.

Coun Fletcher said: "This has got to be looked into very carefully and when the problem has been identified it has to be put right as soon as possible.

"We do not want a repetition of the incident when a wagon coming through Eaglescliffe jumped the rails, and sent ballast flying over the side of Yarm viaduct.''

A resident of Highfield Drive, Eaglescliffe, who did not want to be named, said yesterday: "We were very concerned when we saw a gap in the ballast. We saw the trains vibrating as they passed through and rang Railtrack at York.

"Jarvis has been working on the line for the past two days and we should see if what they have done has done the trick.''

Residents have complained for years about vibrations from trains shaking houses.

It emerged at the weekend that Railtrack is considering increasing the volume of freight trains using the line.