(Reuters) - Merck & Co Inc recalled a batch of vaccines for measles, mumps, and rubella after it accidentally shipped doses to its U.S. customers before internal company approval for market release, U.S. health regulators said.

An investigation by Merck concluded that there were no product safety, quality, or efficacy concerns associated with the batch, the U.S. Food and Drug Administration said on its website.

There would be no impact to the supply of the vaccine, and Merck had contacted customers directly to provide instructions on how to return the product, the statement said.

(Reporting by Adithya Venkatesan in Bangalore; Editing by Supriya Kurane)