McIlroy shares early lead at PGA BMW Championship
Rory McIlroy of Northern Ireland reacts to a putt on the fifth green during the first round of the BMW Championship, at the Cherry Hills Country Club in Colorado, on September 4, 2014 - by Jamie Squire
Four-time major winner McIlroy on Thursday rolled in four birdies in a five-hole stretch around the turn at the $8 million PGA Tour event at the Cherry Hills Country Club course.
There were nine players still on the course when the horn sounded for the end of play.
World number one McIlroy is aiming for his fourth win of 2014 which includes major titles at the Open Championship and the PGA Championship.
US Open champion Martin Kaymer is one of nine players tied at two under. He stands alongside Spain's Sergio Garcia, Canada's Graham DeLaet, Matt Every, Billy Horschel, Kevin Chappell, Russell Henley and Chesson Hadley.
Sweden's Henrik Stenson is also two-under par and was on the 18th hole when play was suspended. He will finish his round early Friday.
Justin Rose, who won this event two years ago, managed a one-under 69. He was joined there by Erik Compton, South Korea's K.J. Choi, Charles Howell, Ryan Palmer, Chris Stroud and Hideki Matsuyama, of Japan.
Jerry Kelly and 2008 champion Camilo Villegas are also one-under par, but have two holes and one hole to remaining their opening round.