DJURGARDEN fans who acquired tickets for the home section of Stamford Bridge during Thursday’s Conference League semi-final second leg constituted “the most serious breach of stadium security in recent memory,” according to the Chelsea Supporters’ Trust (CST).

A large number of supporters of the Swedish club were seen jumping over barriers separating the home and away sections in order to join travelling fans seated in the Shed End, which typically houses away fans.

There were also large groups of Djurgarden fans, possibly up to 1,000, who remained in the West Stand during the match which led to stewards relocating home supporters seated there and the deployment of additional policing.

CST set up a forum on Thursday for supporters to submit evidence which will be shared with the club, and called on Chelsea to investigate how so many away fans were able to purchase tickets in the wrong section, as well as the club’s security response.

The travelling fans seated in the correct section created a raucous atmosphere despite their team losing 1-0 on the night to exit the tournament 5-1 on aggregate.

CST said: “No supporter should feel unsafe while at Stamford Bridge, and the CST will do everything to ensure that a full and proper explanation is issued to supporters and safeguards are put in place to ensure that this situation is not repeated in the future.”

Chelsea confirmed via social media on Thursday night that supporters in the home section had to be moved and that their ticketing policy had been “violated” by fans of the Swedish club.

A club statement said: “We will be reviewing all ticketing arrangements following this evening’s match and commit to implementing all necessary changes following this review.”

Uefa is understood to be awaiting reports from the match before assessing any potential next steps.

Sources close to European football’s governing body pointed out that ticketing for the match was Chelsea’s responsibility.