The operators of the Hawk-Eye system, which rules on goal-line incidents in the Premier League, have apologised after failing to recognise a Sheffield United goal in their Premier League clash with Aston Villa.

Technology was thrust back into the spotlight as visitors United were denied a clear goal at an empty Villa Park during the first half of their 0-0 draw, when Villa goalkeeper Orjan Nyland carried the ball over the goal-line just before half-time.

It was a major get-off for Villa as the referee's wrist watch, which is linked to the Hawk-Eye system, failed to indicate a goal and VAR official declined to step in.

In a statement Hawk-Eye innovations acknowledged that the ball had crossed the line and blamed the incident on cameras being 'occluded' by Nyland, the goalpost and a Villa defender.

The statement read: "During the first half of the Aston Villa v Sheffield United match at Villa Park, there was a goal-line incident where the ball was carried over the line by Aston Villa goalkeeper no 25. Nyland.

"The match officials did not receive to the watch nor earpiece as per the Goal Decision System (GDS) protocol. 

"The seven cameras located in the stand around the goal area were significantly occluded by the goalkeeper, defender and goalpost. This level of occlusion has never been seen before in over 9,000 matches that Hawk-Eye Goal Line Technology has been in operation. 

"The system was tested and proved functional prior to the start of the match in accordance with the IFAB Laws of the Game as confirmed as working by the match officials. The system has remained functional throughout. 

"Hawk-Eye unreservedly apologises to the Premier League, Sheffield United and everyone affected by this incident."

Chris Wilder (C) states his case to referee Michael Oliver

Sheffield United boss Chris Wilder insisted it had been clear the ball was over the line.

"It was in the Holte End, the goalkeeper was in the Holte End and eight rows back. Everyone knew it, saw it and felt it," he said.

"I don't know whether to laugh or cry. Already the jokes have started, I've just seen Del Boy with a Hawk-Eye watch on. It's all going to come out but we're pretty disappointed and we've got to get on with it.

"I believe a decision should have been made from Stockley Park (the VAR centre). For someone to tell me with seven cameras and this is the first time it's happened in over 9,000 games it's a difficult one to take.

"We've got Chris Kavanagh (fourth official), one of the best referees in the Premier League and Michael Oliver possibly one of the best referees in Europe and if you ask them they'll be scratching their heads over how this situation occurred.

"We believe it should have been referred (to VAR)."

A statement from the Professional Game Match Officials Board explained why VAR did not intervene when the technology failed.

It read: "Under the IFAB protocol, the VAR is able to check goal situations, however due to the fact that the on-field match officials did not receive a signal, and the unique nature of that, the VAR did not intervene."

Aston Villa boss Dean Smith admitted his side got lucky.

He said: "We controlled the first 30 minutes but we got away with one, certainly, with the technology not working. But I've been in the other position where technology has not been good for us at times.

"There's always going to be some error, we have human error from officials and we have to accept that.

"There's going to be errors in technology as we've seen with VAR this season and now for the first time ever with Hawk-Eye. We just have to accept it and move on, there's nothing else we can do.

"We're the ones who go away disappointed even with that controversy. The fact that we are just shows that the performance was good. We need to maintain that level."