World number three Cameron Smith headlines a six-way tie atop the Memorial Tournament leaderboard after Thursday's first round at Muirfield Village.

Smith is joined by American trio Luke List, Cameron Young and Davis Riley, as well as Canada's Mackenzie Hughes and South Korea's Lee Kyoung-hoon.

It is the largest leading group after the first round in tournament history, but they all got to their five-under 67 in different ways. 

Young finished the day second in average driving distance (316.8 yards), behind only Jon Rahm, while Lee, Hughes and Smith finished top-six in putts-per-green-in-regulation.

List was the only member of the leading group to finish with less than two bogeys, and Riley played an all-round game; top-15 in driving distance while being dialled in with his putter down the back-nine, going five-under from the 11th hole to the 17th.

US PGA Championship runner-up Will Zalatoris is part of the three-man group one stroke off the lead, while Max Homa and Canada's Corey Conners are in the logjam at three under.

A star-studded group finished with a two-under 70, including Rory McIlroy, Jordan Spieth, Xander Schauffele and Im Sung-jae, while Chile's Joaquin Neimann is with Collin Morikawa and Jason Day at one under.

Patrick Cantlay and Rahm were even-par, Mito Pereira will need a solid second round to make the cut after a one-over finish, and Hideki Matsuyama was handed his first career disqualification for using a wood with paint on its face – deemed illegal. He was three over at the time of the incident.