Jordan Spieth at 12 hits a lovely little bit of draw off the tee - but he doesn't get the kick off the apron that he wanted. He is short by a good 30 yards.

Jason Day caught a flier at the 16th by the way. His tee shot came streaking through the green registering 370-odd yards. Monster. He looked like he may have pulled a leg muscle crashing out that shot.

He limps down to check his lie and manages to smuggle out a par, with his birdie putt coming up just short. He stays two under.

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Branden Grace's score is dented by a bogey at 12. He is back to four under and suddenly playing partner Dustin Johnson has a two-shot lead.

This stock market has got very jumpy.

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Dustin Johnson picks up his birdie at 12 to move to six under and take exclusive control for the lead.

Jordan Spieth's wayward tee shot on 11 has landed him with a bogey that takes him to three under.

Jordon Spieth with a lovely touch to land his second on the 11th green.

Meanwhile Branden Grace on the par-four 12th has a roller-coaster green to negotiate for a birdie.

But he has been cowed by the fear of hitting past. That is nowhere near and he has 12-15 feet to make for par.

Dustin Johnson also a little limp with his eagle putt. The greens are releasing gremlins in these players' brains.

Thanks Peter.

We join Branden Grace who has strapped on his crampons to clamber down one of Chamber Bay's vertiginous banks.

He ends up standing below the ball, gripping the club about halfway down the shaft and punching out a decent recovery onto the green. That was his second on the par-four 12th.

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Jason Day with a carbon-copy of Shane Lowry on 15. Can the Australian knock in a birdie?

Lowry is already teeing off on the 16th and he's pushed that into the long fescue grass down the left.

Jordan Spieth crashes a drive down the 11th and straight into a fluffy mound or rough that sits right in the middle of the fairway. A few yards left or right and he would have been fine.

Branden Grace in trouble down the right of 12, asking his ball to "get lucky". It doesn't.

It's all getting a little nervy out there and here's Mike Henson to take you through to the close of play...

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Shane Lowry's birdie putt doesn't want to drop so it's only a par on the 15th for the Irishman.

Dustin Johnson's par putt stays on the 11th green, while Patrick Reed's 33-footer on 10 is also still visible. He then pushes his bogey putt. A third double of the round for young Patrick who goes to +1.

Jordan Spieth trundles in for par to 10 to stay four under.

Patrick Reed from a horrible spot up in the long grass to the left of the 10th green and it's all he can do to hack out on to the far side of the green.

Up on 11 and Dustin Johnson is playing his third with a wedge from off the green. The ball bites a little too quickly and he's got a testing 10-footer for par. Branden Grace from a similar spot gets more roll and he finishes an inch away. They could well be level in a couple of minutes.

Back on 10, Jordan Spieth from 47 feet and he's knocked that three feet by.

Shane Lowry on 250-yard par-three 15th is imploring his ball to fly. It listens and for added good measure takes in a slope at the back of the green and comes to rest eight feet from the pin. An immediate chance to get back to three under for the Irishman.

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Branden Grace hits a low drive down the 11th towards the black smoke from the fire which is smudging the blue sky.

Patrick Reed has found his ball on the 10th and he's deep in conversation with his caddie, trying to pick the right club and strategy because this a completely blind shot.

"Oh no, that's fat and left," says Reed as his ball disappears into more trouble.

From the other side here's Spieth with the ball well below his stance. His ball ricochets off some shrubbery to the left of the green and flicks across to the right but it stays on the short stuff. Think you'd call that a member's bounce.

Dustin Johnson crunched another drive down the par-four 10th but finds a bit of greenside sand with his approach to the green. Careless that. But a superb splash out to a foot and he's staying six under.

Patrick Reed goes way right off the tee on 10, Jordan Spieth is left.

Shane Lowry lags up to six feet but cannot hole the par putt on 14 and he's dropping to two under.

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Shane Lowry is ticking along nicely. Another par on 13 to stay three under. He's through the back of 14 and will need a good up and down from there.

Back on nine and Jordan Spieth found the sand with his tee shot. He splashes out to about 10 feet and he'll have a similar one to Branden Grace which drifted right late on. That was a complete mis-read from Spieth and he is dropping to four under. A real up and down front nine.

Patrick Reed from the middle of the green and he is short of pace up the hill from 20 feet. A 12-inch par-putt for a four-over opening nine.

-6 D Johnson (US) 9; -5 J Speith (US) 7, B Grace (SA) 9; -3 S Lowry (Ire) 13, -2 J Luiten (Ned) 9.

Selected others +4 P Casey (Eng) 15, R McIlroy (NI) F, I Poulter (Eng) F; J Rose (Eng) F; +7 C Montgomerie (Sco) F, L Donald (Eng) F, L Westwood (Eng) F; +10 P Mickelson (US) F

For a full leaderboard, click this way, external.

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There's a big fire at the Marina a couple of miles down the coast and there's a thick plume of black smoke billowing into the air and heading Chambers Bay way.

Dustin Johnson finds the dancefloor on the short ninth and he nonchalantly rolls in for birdie to get to six under par - two under for his front nine.

Branden Grace is struggling after missing the green and leaving his second 10 feet from the cup. His effort is centimetres wide and he drops back to five under.

Dustin Johnson is our new leader folks.

Patrick Reed chops his ball up on to the green and he uses the slope at the back to get the ball to roll back towards the flag but it's not stopping and he'll have a 20-footer for birdie. He nudges that a couple of feet past.

Spieth's chip up leaves him four feet for par but he doesn't set that out far enough right and that's just a par.

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Jordan Spieth and Patrick Reed both leak their approaches to the eighth out right. Spieth is not quite so wild and he will have a chip from the short stuff. Reed is chuntering to himself as his heads down towards Dustin Johnson country.

Jay Townsend
Former American professional golfer on BBC Radio 5 live

The players have been less than complimentary about Chambers Bay but Jay Townsend is sticking up for the course: "There is a lot of ego involved.

"If the players played this course a lot more and played the US Open here again the reactions would be a lot different they would know what to prepare for and know what to expect.

"I think that if they don't come back to Chambers Bay because of the greens they will never go back to Pebble Beach and Torrey Pines again either."

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Shane Lowry with a decent two-putt for par on 11, while back on eight and Branden Grace lags his eagle putt to three feet. He could go top of the shop on his own shortly.

Dustin Johnson takes a couple of long looks at his six-footer but he still doesn't get the read. Safe par to remain five under.

Up steps Grace and that is slap, bang right in the middle of the cup. We have a new leader.

Dustin Johnson gets free relief for a reason I don't fully understand. But, under the close guidance of a rules official, he is allowed to pick up and drop no nearer the hole. He is directed towards the side of a hill and after two drops that predictably dribble away from him, he is allowed to place his ball.

He dinks his chip 30 feet over the pin and the slope does the rest. Short birdie attempt coming up after all that kerfuffle.

Up on eight and Dustin Johnson overcooks his mid-iron approach to the par-five green. It ends up back right but doesn't fancy the view so trundles off down a cart path and is only halted by a muddy, sandy concoction. Big error from the big hitter.

Over on the driveable par-four 12th and Shane Lowry plays a sensible lay-up but then comes up short with his wedge into the green and he's left with a 40-footer for birdie.