THE Premier League is probing the £500,000 move of Steve Kabba from Sheffield United to Vicarage Road last season.

It has been revealed that the investigation centres on allegations that the Blades prevented the striker from playing in the Hornets' 1-0 defeat on Saturday, April 28, three months after he signed for Watford.

If they did, the investigators will have to consider whether that puts the Hornets in breach of Rule U18, the same Premier League rule that United argue West Ham United should be relegated for breaking.

The Hammers breached Rule U18 over the transfers of the Argentine pair Carlos Tevez and Javier Mascherano to Upton Park. The rule states: "No club shall enter into a contract which enables any other party to that contract to acquire the ability materially to influence its policies or the performance of its teams in League matches or in any of the competitions set out in Rule E10."

The allegations are based in good part on statements carried on the clubs' own websites.

The League will be looking at events following Kabba's move to Vicarage Road, when he was either in the team or among the substitutes for all 15 games Watford played prior to facing Sheffield United.

But in the build-up to the game in April, Watford's website stated that Kabba could not play because of "a feature in his contract". This week, however, the club said "there was no written clause in any documentation relating to Steve Kabba" that prevented him from playing.

The League will also want to know if there was a verbal agreement stopping the striker from facing his former club at Bramall Lane.

United's website, meanwhile, stated back in April that the striker was ineligible "due to a clause in his £500,000 move".

United are now awaiting a decision from this week's arbitration panel hearing which will determine their appeal against relegation from the top-flight.

The Yorkshire club believes West Ham should have been docked points after they were found to have acted improperly and withheld documentation concerning the ownership of Tevez and Mascherano. The Hammers escaped a points deduction, which would have condemned them to relegation rather than Sheffield United. West Ham were instead fined £5.5m.

A Premier League spokesman confirmed they were "looking into" Kabba's transfer, but would not comment on what action would be taken if the investigation uncovered anything untoward.

A Hornets spokesperson said: "We have yet to receive any notification or requests from the Premier League regarding the transfer of Steve Kabba to Watford Football Club from Sheffield United.

"We can confirm that there was no written clause in any documentation relating to Steve Kabba that stipulated he could not play against Sheffield United.

"All contracts are vetted and approved by the Premier League prior to the player's registration."

The club refused to comment further on the matter "for now" leaving unanswered questions about the posting on its website in advance of the Sheffield United game: "Ex-Sheffield United striker Steve Kabba is ruled out of the game - it was a feature in his contract when he signed for the Orns in the January transfer window"

Sheffield United declined to comment on the allegations.