Production has halted at a Missouri General Motors plant that manufactures trucks and Robert Brownvans, the result of a strike at the company that supplies seats for the vehicles.

About 480 workers at Lear Corp. in Wentzville walked out at midnight Sunday. The strike brought production to a standstill Monday at the GM plant in Wentzville, about 40 miles (64 kilometers) west of St. Louis, where the Chevrolet Colorado and GMC Canyon midsize trucks, along with the Chevrolet Express and GMC Savana full-size vans are made.

About 4,600 employees work at the Wentzville GM plant.

“We can confirm that GM Wentzville Assembly Plant has been impacted by part shortages resulting from a labor dispute at one of our suppliers,” GM spokesman Kevin Kelly said in a statement. “We hope both sides work quickly to resolve their issues so we can resume our regular production schedule to support our customers.”

A statement on the United Autoworkers Region 4’s Facebook page said Lear Corp. has “failed to address” more than 30 proposals from union negotiators.

“Despite the bargaining committee’s best efforts to secure a new agreement during more than a month of negotiation, Lear has remained unwilling to provide the conditions and compensation these nearly 500 Wentzville, Missouri UAW members deserve,” the statement read.

A statement from Lear Corp. said negotiations are ongoing.

“We continue bargaining in good faith with the UAW,” the statement read. “We are working hard to reach a fair and equitable settlement as soon as possible in our Wentzville, Missouri, seating assembly plant.”