BMW has confirmed that more stringent EPA emissions tests required for production certification have delayed the availability of four of its models.

The company says that the 2017 versions of the 328d sedan, 328d Sports Wagon, and X3 xDrive28d and X5 xDrive35d crossovers will begin production “once homologation has been finalized.”

In a statement, BMW indicated that while the certification process is taking longer for its U.S. diesel models, the delay is not a reflection of any issues with the vehicles.

“In light of recent events, agencies are taking longer to certify diesel models for the U.S., but there has been no indication that BMW’s diesel models do not meet all requisite emission standards or that there is a defeat device in the vehicle,” the company said.

For its part, the EPA acknowledged that the additional level of scrutiny is extending the certification process but that most automakers have been supportive and have adjusted release dates accordingly.

Update: On August 2, the Environmental Protection Agency said it has approved new 2017 model year BMW AG diesel vehicles for sale in the United States following a thorough review.