An investigation is underway after a schoolgirl suffered an electric shock while walking near light rail construction in the CBD.

The 15-year-old had taken off her uncomfortable shoes and was walking in wet socks in the city.

She was near a light rail construction zone when she was suddenly shocked at the intersection of Ultimo Road and George Street.

Passersby who tried to help say they were also zapped.

The girl was taken to hospital for cardiac assessment.

Transport Minister Andrew Constance has since apologised to the mother of a teenage girl.

The RMS says it’s investigating and staff have now made the area safe after identifying an exposed wire.