A total of 12 players shot 3-under or better in the opening round and 19 players are within three shots of the lead heading into Friday's second round.
Defending champion Connor Howe is four back after opening with a 1-under 70 on Thursday.
Starting on the 10th hole of Wigman's Gold Course, Lorenz, who hails from nearby Peoria, picked up five birdies on his first nine holes, including four in a row beginning on his fourth hole of the day, and turned in 32. Back-to-back bogeys on his ninth and 10th holes dropped him to 3-under for the day but the Oklahoma junior picked up two birdies on his inward nine to sign for a 66.
Nyfjäll, who plays collegiately at Northwestern, began his round with back-to-back birdies on the 10th and 11th holes and added an eagle 3 on the par-5 14th, his fifth hole of the day, to quickly move to 4-under on the day. He moved to 6-under after collecting his fifth birdie of the day on his 14th hole but gave a stroke back on the 16th and settled for a 67.
Lucas, who attends the University of the South in Sewanee, Tenn., had seven birdies and just two bogeys on his card while Fiorini and Jones shot bogey-free rounds of 67.