Alex Smalley and Hayden Springer lead the way on 14-under-par.
The action continues at the Zurich Classic in New Orleans today.
Offaly's Shane Lowry reeled off four successive birdies early in his opening round with Brooks Koepka - they sit on six-under.
Seamus Power got off to a solid start in his partnership with Matti Schmid.
The pair combined for an opening round of nine under, and will return to the course at around 7pm Irish time.
The American duo of Alex Smalley and Hayden Springer lead the way after Day One, on 14-under.
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