World number one Vijay Singh kept up his red-hot form when an eight-under-par 64 gave him a three-shot lead after an incomplete first round at the $4.2 million Pennsylvania Classic on Thursday.
The 41-year-old Fijian is chasing his fifth victory in six tournaments, and his third this month after landing the Canadian Open and Deutsche Bank Championship.
Sweden's Richard S Johnson, Pat Perez, Cameron Beckman, Ben Curtis and Australian Robert Allenby shared second place on 67 at Nemacolin Woodlands Resort's Mystic Rock course.
South Korean Kevin Na was also five-under after 14 holes when play was halted due to darkness, with 36 players still to complete their rounds.
Jonathan Byrd, Lee Janzen, Tommy Armour III, John Daly, Joey Sindelar and JP Hayes were in the clubhouse on 68. Kris Cox was four-under through 14 holes.
FLAWLESS GOLF
Singh, who took over from Tiger Woods as world number one two weeks ago and promptly went out and won in Canada, played flawless golf on Thursday.
After play began nearly 75 minutes late because of fog, Singh hit 13 of 14 fairways, 17 of 18 greens in regulation and totalled 28 putts.
"I'm driving the ball the way I want it," Singh told reporters after notching an eagle and six birdies.
"I don't know if I can hit it any better. My playing is pretty good. I'm doing the same thing over and over again.
"Today I was pretty close (to perfection)...I'm swinging the club as good as I think I can."
Singh single-putted eight holes on Thursday, including his eagle effort at the par-five fifth. His birdies came at the second, eighth, ninth, 13th, 16th and 18th.
The 6-foot-2 Fijian has already won seven times on the PGA Tour this season, at the Pebble Beach National Pro-Am, Houston Open, New Orleans Classic, Buick Open, PGA Championship, Deutsche Bank Championship and Canadian Open.
Woods pulled out of this week's event, citing fatigue.