American duo Pat Perez and Andrew Loupe and New Zealand's Danny Lee were tied for the lead after day one of the Valero Texas Open was suspended late on.
The start of the tournament was delayed by two and a half hours due to thick fog before Perez and Loupe moved to the top of the leaderboard when play did get under way after both carded 68s at TPC San Antonio.
Rookie Loupe joined the pair on four under par but he must complete his round on Friday morning after being halted following his 11th hole due to darkness.
It was an eventful day for the 25-year-old from Louisiana, who made six birdies and two bogeys after starting on the back nine.
Compatriot Perez had just one blemish on his scorecard, at the par-four 15th, although he followed that up with three successive birdies to close his round in emphatic style.
"I feel as confident as I ever have with my ball striking and where the ball is going to go and if I can make a couple putts, I feel like I can shoot a pretty good score," Perez said on the PGA Tour's official website.
Lee was level par for his round after 13 holes but also hit form in the closing stages with four birdies in his final five holes.
"I'm really believing in myself and I know I can do this," said Lee, who achieved his best ever result on the PGA Tour earlier this month with a second place finish in the Puerto Rico Open.
Chesson Hadley, who pipped Lee to victory in Rio Grande, was one of six players on three under par, while former major winners Zach Johnson, Ben Curtis and Jim Furyk are among those a shot further back.
Defending champion Martin Laird made three birdies and as many bogeys in his level par round, but it was a day to forget for world number five Phil Mickelson, who finished on five over par.