The Scarborough RT will remain closed for at least three more weeks as the Toronto Transit Commission continues its investigation into the cause of Monday’s derailment.

The TTC announced the extended closure of the SRT on Thursday, saying the decision to resume service on Line 3 will be made once the review is complete.

On the evening of July 24, a southbound SRT train was leaving Ellesmere Station when the rear car came off the tracks 500 feet from the station. The cause of this incident is unknown.

There were 45 passengers on the train during the incident, five of whom were taken to hospital with minor injuries.

In Thursday’s news release, TTC CEO Rick Leary said the agency has enlisted the support of leading rail, infrastructure and vehicles experts to assist in the investigation to ensure that “we are leaving no stone unturned.”

“Safety is paramount to all we do and only once we know exactly what happened can we make a decision about the future operations of this line. In the meantime, we are making contingency plans to ensure we are providing the people of Scarborough with frequent and reliable transit options,” Leary added.

The TTC said it is also inspecting the entire SRT fleet and the line’s structural integrity, and those results will also be taken into consideration on when the line will reopen.

Meanwhile, frequent bus shuttle service will continue to run while the SRT is out of service.

“I want to thank Scarborough residents for their patience as the TTC continues to investigate this very serious incident,” Mayor Olivia Chow said in a statement. “The safety of the public transit system is everyone’s top concern and the SRT service can only return when we know it is safe to do so.”

The SRT is scheduled to be decommissioned in November and will then be replaced with shuttle buses until the completion of the Scarborough Subway Extension.

Following the derailment, a spokesperson for the TTC said an early decommissioning of the line is “very much on the table.”

- with files from Katherine DeClerq