"I appreciate your work and attention to the Montana Rail Link derailment in Stillwater County. Your responsiveness over the weekend and thoroughness in investigating the incident is appreciated. I write today to express my concern and to request more information as the investigation continues," the letter said on Monday.
The letter was addressed to US Transportation Secretary Pete Buttigieg, Environmental Protection Agency Administrator Michael Regan and Federal Railroad Administration head Amit Bose.
The letter requests the officials provide information on the cause of the bridge collapse, including whether regulations were followed and whether the bridge was inspected or renovated.
The letter also requests information on whether the contaminants released into the river system - molten sulfur and asphalt - pose substantial threats to the local population or wildlife.
Moreover, the letter asks the officials to provide a timeline for the expected bridge repair and cleanup effort, a list of precautions to mitigate the release of contaminants, and information on how supply chain disruptions are being addressed.
Rosendale also urges the federal officials to work with state and local counterparts as they conduct their investigation and cleanup, the letter said, adding that it is "vital" that the public remains informed on all developments.
The letter requests responses to the questions by July 7 and as more information becomes available.