Ontario Power Generation is suspending further work on the conversion of the Thunder Bay Generating Station to burn natural gas instead of coal.
OPG said no more work will be done until the Ontario Power Authority does a review of electricity needs in northwestern Ontario.
More time is needed to explore other options for electricity supply in the northwest, a news release said on Thursday.
The plant continues to operate, using coal.
Union Gas said it has spent about $5 million toward the construction of a gas pipeline through the city to the OPG plant on Mission Island.
Spokesperson Andrea Stass said Union Gas will be seeking compensation from OPG for those expenses.