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Amtrak has deployed heavy-duty netting to block rock slides from tumbling onto railroad tracks, but not in Vermont, where falling rocks caused a derailment Monday, the rail agency's top official said.

But it's unclear if such a device would have prevented the accident, which injured seven people and disrupted service between northern Massachusetts and Vermont, Amtrak CEO Joseph Boardman told reporters in Tuesday in Montpelier, the Vermont capital.

The devices are called slide fences, and they're similar to nets commonly seen alongside mountain highways. The railroad versions have sensors that relay alerts to approaching trains.

Amtrak only uses them in New York, Boardman said.

"Whether it would work here or not it is unclear, I don’t know," he said.

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Officials also announced Tuesday that all seven people hurt in the crash train had left the hospital.

And they expressed hope that Amtrak service would be restored to the state by this weekend — after investigators finish examining the crash site and the tracks are repaired.

The National Transportation Safety Board will determine the official cause of the accident, but Vermont Gov. Peter Shumlin has already said human error was not to blame for the train's jumping tracks in the town of Northfield, about 10 miles south of Montpelier, the state capital.

Responders stand near railroad tracks at the scene of an Amtrak passenger train derailment in Northfield, Vermont. Stefan Hard / Barre-Montpelier Times Argus via AP

Boardman joined Shumlin at a Tuesday news conference, but he declined to address the cause.

He said he was feeling "very blessed and thankful" that there weren't more extensive injuries.

Five passengers and two crew members were hurt when the southbound train, called "The Vermonter," derailed Monday morning after hitting fallen rocks, officials said. The engine and the first passenger car tumbled into a brook.

All those patients have been released from hospitals, including the most seriously injured, an assistant conductor who suffered a concussion, Shumlin said.

Once investigators finish their work at the scene, the cars will be removed from the scene and crews will begin replacing damaged track, Shumlin said.

"Our hope is to have the Vermonter up and running in days, not weeks,” the governor said. The earliest possible date would be this weekend, he added.

In the meantime, Amtrak replacing Vermonter service north of Springfield, Massachusetts with buses.