(Bloomberg) -- General Motors Co. has delayed starting a second production shift at two pickup plants in Michigan and Indiana as the manufacturer struggles to procure enough parts.

The largest U.S. automaker originally planned to run two shifts next week at the truck plants and a sport-utility vehicle facility in Lansing, Michigan, according to a spokesman. While the SUV facility remains on track, GM’s suppliers in Mexico have been resuming work more slowly than those in the U.S. and may need about a week to catch up.

The delay will further crimp supply of GM’s redesigned Chevrolet Silverado and GMC Sierra pickups and is the latest supplier-related disruption to hit automakers that have been restarting operations this month following weeks-long shutdowns. Ford Motor Co. and Daimler AG’s Mercedes-Benz have had to pause some U.S. production because of parts shortages.

“There is strong demand for our full-size pickups and we will look to add capacity as quickly as we can,” said Dan Flores, GM’s spokesman.

Read more: The U.S. Auto Industry Is Restarting After Covid—Now What?

Ford paused production for the second time in as many days at its Explorer SUV plant in Chicago earlier this week after a worker at a nearby supplier facility tested positive for Covid-19.

For GM and Mercedes, the issue has been Mexico’s restart. The nation’s government has issued conflicting and vague decrees on what factories need to do before they’re allowed to reopen, contributing to delays that have slowed production at U.S. factories reliant on imported parts.

GM reopened its engine and transmission plants in Ramos Arizpe and Silao on Thursday.

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