Man killed in NSW mountains crash

A man is dead and a teenager is seriously injured after a crash in the NSW Blue Mountains.

Police say a car towing a trailer lost control on Bells Line of Road at Mount Tomah about 11.30pm (AEDT) on Sunday.

A man travelling in the car died at the scene while a 16-year-old boy was taken to Nepean Hospital with back and neck injuries.

Investigators are trying to establish what led to the crash, but traffic diversions in the area have been lifted.