Melbourne train passengers whose journeys were disrupted by a fault on the Cranbourne, Frankston and Pakenham lines on Monday will be able to get their tickets refunded.

Services returned to normal on Tuesday morning, after crews spent the night completing repairs for a train fault.

Public Transport Minister Melissa Horne has asked Public Transport Victoria for an investigation.

“I want to apologise unreservedly to all the passengers caught up in yesterday’s incident,” Ms Horne told reporters.

“The hot weather, the disruption that occurred, was completely unacceptable, especially after having to put up with two weeks of disruption on the Cranbourne Pakenham lines.”

Ms Horne says disrupted Cranbourne, Pakenham and Frankston passengers will be able to get a refund.

Gippsland commuters will be eligible for a refund and an extra day of free transport travel, given they have dealt with more than 100 days of disruption over recent months.

Public Transport Victoria CEO Jeroen Weimar said the incident was caused by an overhead failure near Malvern station but exactly what prompted it remains under investigation.

“We take this very seriously. It’s rare to get this scale of disruption on our network. It’s completely unacceptable and we’ll be working very closely with our operators to ensure we understand the root causes for this and that it can’t happen again,” he told reporters.

Opposition transport spokesman David Davis said commuters deserved a system they could rely on.

“Daniel Andrews and his ministers have not been able to deliver a reliable safe network and a network that delivers trains on time,” he said.