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NEW YORK (CBSNewYork) — The Metropolitan Transportation Authority has pulled roughly 300 brand new subway cars from service over a safety concern.

New York City Transit Authority CEO Andy Byford said Wednesday two recent incidents “raised questions about the reliable operation of a door mechanism” on the new Bombardier R179 cars, CBSN New York’s Aundrea Cline-Thomas reported.

There have been no injuries related to the issue, and the cars were pulled for inspection out of an abundance of caution.

The cars were replaced by spares for the morning commute. The only line that was impacted was J/Z, Byford said.

The pulled cars represent about 5% of those the MTA has operating.

CBS2 has previously demanded answers about mechanical issues impacting the new cars. At the time MTA officials said the issues were routine with new fleets and ensured that it was working with Bombardier to address the issues.

Byford, who has previously criticized the manufacturer, said the MTA “finds this latest development unacceptable. We intend to hold the company fully accountable.”

Bombardier said in a statement that two doors on cars failed to function as intended, and said they were not properly calibrated by the door supplier.

“We are now inspecting all of the R179 cars and, where necessary, making adjustments to ensure the safe and reliable performance of the doors for the entire fleet,” Bombardier said in a statement. “We value our partnership with New York City Transit and are fully committed to providing high quality, reliable, safe rail cars for the millions of people who ride New York’s subway system every day.”

According to the MTA, a warranty covers the cost of modifications for two years after the cars are delivered.