Another NWSL club, North Carolina Courage, sacked the Englishman as their coach last week after the allegations.

Riley, who won back-to-back NWSL championships in 2018 and 2019 with Courage, has denied the accusations.

On Monday, Thorns team owner Merritt Paulson said Riley had been suspended from his coaching role at the club in 2015 after a complaint over his behaviour.

He said the club shared the results of its investigation with the NWSL at the time but had been "opaque" with the public over the issue.

"[We] made an opaque announcement about not renewing Riley's contract as opposed to explicitly announcing his termination, guided by what we, at the time, thought was the right thing to do out of respect for player privacy," said Paulson, whose Peregrine Sports also owns Major League Soccer side Portland Timbers.

"I deeply regret our role in what is clearly a systemic failure across women's professional soccer."

Riley was sacked by North Carolina Courage after an investigation by The Athletic, who spoke to more than a dozen players he had coached since 2010.

Paulson said the team would co-operate with all investigations and were implementing an anonymous reporting system for harassment and discrimination.

The NWSL's board of governors and US Soccer have launched investigations into the matter. The NWSL launched a new executive committee after sacking commissioner Lisa Baird on Friday.

All NWSL games at the weekend were postponed as a result of the allegations.

World governing body Fifa has opened a preliminary investigation "due to the severity and seriousness of the allegations being made by players".

High-profile players including two-time World Cup winners Alex Morgan and Megan Rapinoe have demanded changes across the league.