Updated

By Julian Linden

KOHLER, Wisconsin (Reuters) - Thick fog delayed the start of the second day of the 92nd U.S. PGA Championship at Whistling Straits on Friday, putting the tournament further behind schedule.

More than three hours of golf was lost because of fog on Thursday and 78 players were unable to complete their first rounds because of fading light in the evening.

It was hoped some time would be made up with an early start on Friday but the conditions prevented that.

Organizers were not able to say when play would start but the delay was likely to be lengthy.

"Once the fog has lifted and it is clear to play, the first starting time will be 30 minutes following that time," officials said.

When play does begin the first round will be concluded before the second round commences, raising the possibility that the second round will not be finished until Saturday.

Among the players still on the course on Thursday night were Phil Mickelson and Ernie Els.

Tiger Woods, whose world number one ranking is under threat following the worst PGA Tour performance of his career last week, was among the early starters on day one and showed signs of improvement with a one-under-par 71.

That left him three behind the clubhouse leaders, American Bubba Watson and Italian Francesco Molinari, and three others still on the course.

(Editing by Tony Jimenez)