Slow moving trains on the tracks by Matua Saltmarsh Reserve should be back to normal service by next week.

It comes following reports from residents that the trains have been crawling along the east end of the Matua estuary for several weeks.

One resident has suggested the trains caused vibrations, which caused his picture frames vibrate against the glass.

KiwiRail has confirmed they are replacing the railtrack in the area.

The replacement work means trains will be running at a lowered speed along the track, until the work has been completed.

'Trains are temporarily running at a reduced speed along a section of the rail line adjacent to Matua Saltmarsh Reserve,” says a KiwiRail spokesperson.

'We expect to have the rail replaced and for trains to return to normal speeds by next week.”