Americans Roberto Castro and James Hahn stayed at the top of a congested and unfamiliar leaderboard after two rounds of the Humana Challenge in California.

The pair were part of a three-man leading group last night and they both produced five-under rounds of 67 to move 14 under overall and keep clear of three of their compatriots, Darron Stiles, Scott Stallings and Richard Lee, who were one stroke behind.

Jason Kokrak, the other member of the leading trio after day one, could only manage a three-under 69 today to sit in a group of nine players on 12 under.

The tournament represents a golden chance for a PGA Tour win with many of the game's leading lights in Abu Dhabi for the HSBC Championship.

Neither Castro nor Hahn could reproduce yesterday's error-free from, but the latter did throw in an eagle at the par-five fifth hole of the La Quinta course to go with four birdies and a bogey.

Castro carded seven birdies against two bogeys on the PGA West Palmer course.

Sweden's David Lingmerth, playing the PGA West Nicklaus course, produced 10 birdies in his eight-under round to sit as the leading European in the group on 12 under.

Alongside him, among others, were Zach Johnson and Australians Greg Chalmers and Aaron Baddeley.

Brian Davis was leading the Briton challenge on eight under, but that was only good enough for a share of 43rd.

A shot further back was Greg Owen, while Martin Laird was six under, Ross Fisher was five under alongside perhaps the tournament's biggest name, Phil Mickelson, and David Lynn four under.

By the end of the second round, 142 of the 156-strong field were under par.