St Helens had to leave Hull KR's Sewell Group Craven Park under a police escort following what the club described as a "terror threat" sent to their Instagram account.
Sky Sports News understands the threat was made towards the St Helens team during their 20-12 Super League semi-final loss.
Saints head coach Paul Wellens was seen speaking to police officers after the full-time whistle.
A police officer was stood outside the coach for the players and staff to get on, with a cordon of eight stationed around the coach earlier.
The team bus was then given a police escort as they departed the stadium.
A spokesperson for the club said in the post-match press conference: "The club had a terrorist threat sent to the Saints' Instagram account.
"It was reported to the St Helens Ground Safety