AB Volvo's shares fell Oct. 16 after the Swedish truck maker revealed that a component used to limit nitrogen oxides emissions was degrading quicker than anticipated.

"All products equipped with the component meet emissions limits at delivery; the degradation is due to a materials issue that occurs over time," the company said in a statement.

Volvo warned that some of its engines could be exceeding emissions limits for nitrogen oxides due to the component failure. It added that the degradation does not appear to affect all vehicles and engines to the same extent, and that it does not pose any product safety issue.

Volvo shares ended the day down 6.20 Swedish kronor, or 4.4%, at 136.25 kronor.

The truck manufacturer said the volume of affected engines or vehicles is still unknown although it estimates that the largest volume of potentially affected engines had been sold in North America and Europe.

The company said it is discussing remediation plans with authorities in the affected markets.

As of Oct. 15, US$1 was equivalent to 8.88 Swedish kronor.