An investigation by the UK’s Guardian newspaper has uncovered cases of betting manipulation by Tennis officials.

The investigation found that at least two umpires were secretly banned by the International Tennis Federation in 2015, with several more officials currently under investigation.

It is alleged that certain umpires on the ITF’s Futures Tour manipulated betting markets by delaying the relay of points information.

The ITF works with sports data provider Sportradar as its official data partner, enabling it to deliver accurate results to the media and information to bookmakers for odds pricing.

According to the Guardian, umpires in the lowest rung of professional tennis deliberately delayed updating the live score system after a point was scored, thereby giving unscrupulous betting syndicates an advantage over bookmakers. In some cases, the umpires are said to have directly texted scores to their accomplices before updating the official system.

Following the revelations, the ITF said that it has updated its code of conduct so that sanctions against officials will be announced publicly as of this year. In previous years the tennis body has been quick to name sanctioned players but has not disclosed information about corrupt officials.