South West Trains said that all services had been brought to a halt by the incident.
The company say they were briefly stopped and were now normal.
Thousands of passengers would have been on trains on that section of line at the height of the rush hour.
More top news
The lunchtime forecast for the west of the region from Holly.
Holly has the lunchtime forecast for the east of the region.
Holly has Monday's forecast for the east of the region.