(Reuters) -The National Highway Traffic Safety Administration said on Wednesday it had closed an engineering analysis on 2,038,307 Nissan Motor vehicles over issues related to rear suspension control arm failure.

The investigation, which covered 2013-2018 Nissan Altima and 2016-2018 Nissan Maxima vehicles, looked into whether the lower control arm of the rear suspension system may separate from the chassis due to corrosion, NHTSA said.

"Nissan acknowledges that a crack can develop in affected control arms due to stress loading from normal use and that salts commonly used for roadway snow and ice treatment may result in corrosion that exacerbates the progression of the crack," the agency added.

The U.S. auto safety regulator said Nissan implemented a design change in January 2018 to improve the durability of the lower control arm.

Some affected vehicles have been repaired with the countermeasure part under a customer satisfaction campaign, while some were provided a warranty extension to 10 years or unlimited mileage from three years or 36,000 miles.

"With a declining trend of reports and Nissan's actions to implement a countermeasure and extended warranty coverage, further investigation of the issue does not appear to be warranted at this time," NHTSA said.