Iain Carter
BBC golf correspondent at Oakmont Country Club

"It's extraordinary. There is a buzz about the place. If Johnson does get a two shot penalty then Garcia, Lowry and Piercy will share the lead with him. I have never known anything like this. As soon as we know, you'll know."

This is bizarre. Did Dustin Johnson ground his club when his ball moved on the green earlier or not?

The officials have said they will review the footage later as far as we know. They have a duty to now tell all players on the course about the situation. This is poor. Surely there must be clarity on this at such a critical stage.

The American has a birdie putt to come on 12.

As Shane Lowry smashes a tee shot onto the fairway on the 12th - a par five - I can tell you Branden Grace is within three of the lead as he made a four on this hole a few moments ago.

Sergio Garcia is over a right-to-left swinger from some way out on 13. He can't can he? He can you know. It takes the break, it's dead weight, hanging on the lip... drops.

What a putt. That's three under and two back as things stand.

Image source, Getty Images

Iain Carter
BBC golf correspondent at Oakmont Country Club

"Well there is something amiss but we're not too sure exactly what. 

"Dustin Johnson was asked if he addressed the ball and he said no, but it looks like he may have done it, without even knowing. 

"Even if his club was on the ground next to the ball and the ball moves, it's his fault.

"The rule officials are meeting now. We'll keep you posted."

As Daniel Summerhays holes out from a chip on 12 to go back to two over we are still waiting for solid confirmation that all is well with Dustin Johnson's scorecard.

Shane Lowry glances across at Dustin Johnson's group from the 11th green. Lowry wants no nonsense, no distractions as he takes on a tricky four footer for par. The ball meanders a little but not much and it nestles in the cup.

From what we can see there's nothing doing for Dustin Johnson and the rules official. Everything seems OK.

Jim Furyk feels he's come up just shy after hitting a four-under 66 to finish the tournament on one under par.

"It was an exciting day and I thought if i could make it to three under I'd have a chance," he told Sky Sports. 

"The last time the US Open was here I made a bogey five on the 17th so it was good to get some retribution with a birdie there today.

"I can see myself finishing third but it was a heck of a try."

Image source, ap

Scott Piercy ladies and gentlemen. Coming up on the rails.

He takes a similar putt to Sergio Garcia on 12, perhaps he's benefited by reading Garcia's line because this ball is good!

That's 40ft and that ties him for second.

Respected golf journalist Brian Wacker is monitoring a potentially controversial situation for DJ?

"Don't spin, don't spin," says Shane Lowry on the 11th fairway. His ball spins on the green and leaves a long putt.

Sergio Garcia is putting for birdie but misses fractionally and stays at two under.

The world number one now in his pink shirt. This putt on 13 is a touch right to left from 14ft. It's on it's way, it's underground. He moves to one under. 

What will the front runner think when he sees Day's name in red numbers on the leaderboard?

Let's not forget that Dustin Johnson had a putt to win the US Open last year.

Then he had a putt to force a play-off. 

Then he missed and Jordan Spieth was champion.

Will the haunting memories of 2015 enter his mind and frazzle it yet?

Image source, AP

Sensational by Jason Day on the par-three 13th. It's straight at the pin, lands softly and he's got a makeable uphill putt from a dozen feet. 

Is Dustin Johnson feeling the pressure? A birdie putt on the 11th from 12 feet. He sets it off a yard right and watches it creep close but not in. A safe four though and he leads by two with a reachable par-five coming up.

It seems crazy to be talking about a player coming from five back. But this is Oakmont. It's brutal out there. Ask Lee Westwood.

Are the wheels coming off for Lowry? His par putt stays left and needs to stop quicker than it does. He's got about the same again to just drop one. He nails it. Big putt that but he needs a birdie run. And quick.

Image source, Getty Images

Shane Lowry takes a look at his putt, from behind the ball, behind the cup, from the side. It will swing from right-to-left. He sets it off a good 15 feet wide and the ball is not coming back enough.

Another testing six-footer for par.

Up on 12 and Jason Day is telling his ball to stay "right there". He knows this chip is going close, so close it's in the hole. Eagle three for the world number one who is suddenly back to level par.

News of Sergio Garcia has gone a little quiet. The Spaniard is still in this though. He is two under for the day and tournament after 11 holes. Just three off the lead.

Dustin Johnson knocks in his par putt on 10 and then finds the centre of the fairway on 11. 

Here is Sergio with his tee shot on the 600 yard par-five 12th. Driver onto the fairway, he may chase one up to the green from there.

Shane Lowry is right on line with his approach to 10 but his ball bites and he's left with a 35-footer down a slippery hill