Scottish Premier League chiefs are to follow in the footsteps of UEFA by investigating allegations that Celtic fans were involved in pro-IRA chanting at the club's ground.
European football's governing body UEFA announced Monday the Scottish giants would be brought before their control and disciplinary body on December 8 to face charges of "illicit chanting" during the 3-1 Europa League victory over Rennes on November 3.
On Tuesday SPL operations officer Ian Blair said league chiefs would also be investigating claims that songs supporting the Irish Republican Army were also sung during a goalless draw with Hibernian at Celtic Park on October 29.
Blair said the SPL's move follows complaints by a former referee and senior policeman, Eddie Smith, to a match delegate.
"Eddie has mentioned that there was pro-IRA chanting but we need to find out more about when it happened and what exactly went on," said Blair.
"We also have to establish that Celtic, as I am sure they will have, co-operated fully with the police in the aftermath of this event."
Celtic said Monday they will co-operate fully with UEFA's investigation.
"We have been made aware of this hearing in a letter from UEFA. We have not been given any detail on the nature of the alleged incidents and have not received any information on this matter directly from the police," a spokesman said.
"Celtic supporters have a magnificent record of positive support for their team, something recognised by both UEFA and FIFA in recent years and we are extremely proud of this reputation.
"Therefore, the club will co-operate fully with any UEFA investigation."
The charge relates to UEFA disciplinary regulation 11.2, namely: "the use of gestures, words, objects or any other means to transmit any message that is not fit for a sports event, in particular if it is of a political, offensive or provocative nature".
Possible UEFA sanctions include a fine and ban on supporters, although Celtic could face a lesser punishment if found guilty as it would be deemed a first offence.
Celtic's Glasgow rivals, Rangers, have been punished on three occasions for "discriminatory" behaviour from their fans.
Celtic are a predominately Catholic club while Rangers fans are mainly Protestants. Both clubs have strong ties to Ireland, where the largely Catholic IRA once waged a terror campaign in its quest for Irish unity.
The British controlled province of Northern Ireland is mainly Protestant while the Republic is largely Catholic.
Celtic last month urged fans to stop singing pro-IRA chants after being "inundated" with complaints from their own supporters following their 2-0 defeat by Hearts at Tynecastle.
Police announced they had launched an investigation into the "singing of sectarian songs" following the Scottish Premier League game on October 2.