Troubled Adelaide trains back on track

An investigation has been launched into a major power outage that crippled some Adelaide trains as services returned to normal on Saturday.

The state's rail commissioner will look into the problems on the Seaford and Tonsley lines which carry about 15,000 passengers each day between the city and the southern suburbs.

The investigation would try to determine what went wrong and how such an issue could be prevented in the future, the transport department said.

Trains were brought to a standstill on the two lines early on Thursday when a circuit breaker tripped at an electrical substation.

But what caused the circuit breaker to trip is still to be determined.

Transport Minister Stephen Mullighan apologised to commuters on Friday, including some who were forced to scramble down ladders to escape disabled railcars and others who were forced to walk along the tracks when their trains stopped between stations.

"I completely understand people's frustration and their anger when the services that they expect to use aren't being provided reliably," Mr Mullighan said.

Substitute buses and diesel rail cars were brought in as the problem stretched over two days.

With services back to normal for Saturday, fans' plans for attending the AFL game at Adelaide Oval and Sunday's A-League grand final were not expected to be disrupted.