DETROIT - Auto plants and other big energy users throughout Southeast Michigan had to shut down or limit operations Thursday due to a natural gas shortage caused by a fire and frigid weather.

At least 18 factories and other facilities run by General Motors, Ford and Fiat Chrysler were affected, although some were starting to resume limited work by the afternoon as the situation improved.

The fire hit a Consumers Energy natural gas compressor station north of Detroit on Wednesday as record-cold temperatures swept over the region.

The state's largest natural gas provider said gas flow from the station was shut off, putting Michigan residents at risk of brief service interruptions in subzero temperatures.

Fiat Chrysler closed its truck assembly plants in Warren and Sterling Heights, Michigan, while Ford reduced operations at two transmission factories and a plant that stamps parts for the hot-selling Ford Ranger small pickup near Detroit. Ranger production was unaffected.

General Motors was hit much harder, suspending operations at factories in Flint, Lansing, Saginaw, Pontiac, Orion Township and Bay City, Michigan. A Flint plant is gearing up for the launch of new heavy-duty pickup trucks. Even General Motors' sprawling technical centre in Warren, Michigan, north of Detroit, was closed and its roughly 20,000 employees were told to stay home. About 30,000 employees were affected at GM alone.

Only factories served by Jackson, Michigan-based Consumers Energy were affected. Plants powered by the region's other utility, DTE Energy, had no disruptions.

Automakers were hoping that the plants can fully return to normal operations, but they weren't sure when that will happen.

By Thursday afternoon, the situation appeared to be easing as Consumers Energy said conservation efforts had reduced gas usage by 10 per cent, stabilizing its ability to supply houses and other buildings. GM reported "limited operations" had resumed at some component plants with parts of the factories open or a limited number of machines working.

But the utility still asked its 1.7 million customers and others to continue to set their thermostats at 65 degrees (18 degrees Celsius) or lower until 10 a.m. Friday — 62 degrees if they are away from home for more than five hours.

"In our 130 years, we've never experienced this kind of demand or these kinds of temperatures," said CEO Patti Poppe. She said the utility had been prepared to supply more natural gas due to the frigid weather until Wednesday's fire at its largest storage and distribution facility in suburban Detroit.

The economic impact of the shutdowns is likely to be small. Automakers usually can make up for a few lost production days by increasing assembly line speeds. Workers will get paid even though their buildings are closed.

"We are assessing the impact on our operations, but we expect the impact will be minimal," GM spokeswoman Kimberly Carpenter said in a statement.

Other businesses also have been affected. Spartan Motors, which makes emergency and other large vehicles, suspended manufacturing in Charlotte, Michigan, near Lansing, idling about 800 workers. It plans to resume work on Sunday evening. Dart Container Corp., switched natural gas boilers to oil and curtailed some operations near Lansing that use natural gas.

Hemlock Semiconductor, with operations in the Saginaw area about 110 miles (177 kilometres) north of Detroit, cut production to help Consumers Energy. Hemlock is a large electricity user.

Poppe appealed Wednesday night for customers to reduce their natural gas usage.

Temperatures in the state early Thursday fell to their lowest levels of the week, with readings around negative 12 degrees (negative 24 degrees Celsius) in the Detroit area and at bitterly cold levels statewide.

No one was injured in the fire Wednesday at Consumers Energy's Ray Natural Gas Compressor Station in Macomb County. The cause of the fire was under investigation. The company said all gas flow from the station was shut off, and that it activated natural gas peaking storage fields to help meet demand.

News from © The Associated Press, 2019