American Xander Schauffele led the way but was being pursued by a host of European Tour players midway through the second round of the WGC – Mexico Championship began at Chapultepec Golf Club.
The 24 year old Schauffele was three under through 13 holes to lead by a single shot on nine under par.
Overnight leader Louis Oosthuizen, Spain's Rafa Cabrera Bello and Thailand's Kiradech Aphibarnrat headed the chasing pack on eight under, with Shubhankar Sharma and Chris Paisley a shot further back making it five European Tour players in the top six.
South Africa's Oosthuizen held a one shot advantage overnight, but could only turn in a level par 36 and Schauffele took advantage with birdies at the 14th and 15th to advance to grab the outright lead.
A seven footer on the first – his tenth – moved Schauffele to nine under, but former Open winner Oosthuizen got up and down from the sand at the driveable second to move to one under for the day and reduce the gap to one.
Cabrera Bello birdied four of his first six holes in a blistering start, and despite a dropped shot at the eighth turned in an impressive 32 to be only one back.
Aphibarnrat started on the back nine and after taking advantage of an excellent tee shot to birdie the 13th, holed a 45 footer for eagle on the 15th to be three under through six holes on the day.
The Thai star continued his fine round with birdies from close range at the 18th and first to move into the outright lead at ten under.
That was one ahead of Schauffele, with Cabrera Bello, Sharma and Sergio Garcia - who tapped in for eagle on the 11th after a magnificent approach - a shot further back.
Oosthuizen set the clubhouse atrget at seven under with a round of 71, having dropped a shot on the sixth after finding water with his second.
