Tomas Soucek tapped home from close range from Jarrod Bowen's cross from the left byline on 13 minutes to give the Hammers the lead, but it was unclear as to whether the ball had gone out of play in the build-up.

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A three-and-a-half-minute VAR check saw the technology look at the best angles possible before awarding the goal, with Arteta revealing the officials told him that the image was "not conclusive" - so the on-field decision stood.

"I haven't seen it, they only thing they [the officials] said was the image was not conclusive," said Arteta in his post-match press conference.

"It's just a shame that the technology that we have is not that clear that we can say it's out of play. It's done, it's gone and there's nothing we can do about it now."

"So what we have to do is without that, win the game, and with the situations we had today, we had more than enough."

Arsenal had 30 shots on goal and 77 touches in West Ham's box - the latter statistic being the most on record since 2008-09 in a single Premier League match for a team who failed to score.

In the end, former Arsenal defender Dinos Mavropanos doubled West Ham's lead after half-time, with David Raya forced to save a Said Benrahma penalty in stoppage time to deny a Hammers third.

However, the post-match talk surrounded the awarding of the first West Ham goal.

This is the second time Arsenal have been involved in a situation similar to this, with Newcastle's winner against the Gunners in November controversially awarded after Joe Willock took the ball near the byline.

According to the written reasons given after Arteta avoided an FA charge for his post-match comments, Willock told the Arsenal players that he had taken it out of play.

Meanwhile, Bowen - the player directly involved in the incident - said it was difficult to tell whether it had gone out.

"I haven't seen it. It's difficult because the ball was in the air," he told Amazon Prime Sport. "It was hard to tell. It would have been easier to tell if it had been on the ground.

"It was really important to get the first goal. We've won tonight. We need to take one game at a time. It sounds boring but we have to keep getting results."

In or out? You decide

How Neville and Carragher reacted

Analysis: Arsenal's January window just got bigger

Sky Sports' Sam Blitz at the Emirates Stadium:

Mikel Arteta may be grateful that Arsenal's 2-0 loss to West Ham came just days before the January transfer window opens.

Thursday's night to forget showed why there are doubts that the Gunners can finish on top come May 19.

Thirty shots without a goal - including two big misses from Gabriel Jesus and little-to-no impact from attacking substitutes Eddie Nketiah, Emile Smith Rowe and Reiss Nelson - raises more questions about whether more firepower is needed, especially a centre forward.

But do Arsenal need a full-back too? Takehiro Tomiyasu is likely heading to the Asia Cup and Jurrien Timber is still on the injury list, which means there's too much focus on Oleksandr Zinchenko - and it's showing.

A poor outing against Mohamed Salah at Liverpool and then unconvincing for West Ham's first goal. Perhaps it may be time to move on from the Ukrainian, especially in the big games.

But what order these two positions sit on the priority list - and whether there are decent enough options out there - is still unclear.