AUGUSTA, Maine (AP) — Maine environmental groups have requested that the federal government suspend the permits it issued to a billion-dollar electricity project for Massachusetts residents, which Maine voters rejected in a referendum last month.

Three groups, including the Natural Resources Council of Maine, wrote a joint letter on Monday to the federal Department of Energy and the U.S. Army Corps of Engineers, seeking to halt the New England Clean Energy Connect project. The 145-mile (230-kilometer) electric transmission corridor would run through western Maine, The Portland Press Herald reported on Monday.

The letter emphasized that the project could not continue because of the Nov. 2 referendum blocked the project that would be used to transmit power from hydroelectric dams in Canada to the New England grid through Lewiston.

Last week, the Maine Department of Environmental Protection suspended its construction license for the project.

The project is being developed by Central Maine Power’s parent company Avangrid. The developers challenged the referendum in court and continued work on the project after the ballot measure was approved, the newspaper said.

Gov. Janet Mills requested that the project suspend all work. The DEP also ruled the company must halt all work unless it is granted permission by the court.