Three women remain in hospital following yesterday's escalator accident at a city train station.

Two of the women are in a serious, but stable condition, while the other is in a stable condition.

13 people were taken to hospital late yesterday after they were caught in a human pile-up that sent people tumbling down the escalator as they tried to access the platform at the Esplanade train station.

The Public Transport Authority has launched an investigation into the incident.

It's understood many of those injured had been attending a mega bingo event in the city.

The PTA has reviewed CCTV footage and says it appears congestion at the bottom of the escalator caused a bottleneck.

A PTA spokeswoman says early indications are that a group of people stopped at the bottom of the escalator which prevented others from stepping off. This led to several passengers falling over one another.

"The escalator was switched off by a passenger pressing the emergency stop switch within 30 seconds of the incident starting." she said.

"It also appears some of the passengers may have been less experienced public transport users and this may have caused them to pause at the bottom of the escalator rather than move down the platform."

The spokeswoman says a full safety check has been carried out on the escalator and no faults have been found.

She says Transperth escalators are operated at a medium speed, which is consistent with Australian standards, and far slower than many other networks around the world.

"We are aware that escalators can represent a risk of injury to the general public but they are necessary part of any major train system around the world," she said.

"They have operated on our network for decades with only occasional minor injuries but no major incidents."