Police Scotland are investigating DNA swabs from a racist letter that was sent to Kilmarnock manager Alex Dyer, while the club are working with the force to identify the individuals involved.
The Scottish Premiership club received a letter on Monday morning following the 2-1 home defeat to Livingston on Boxing Day.
Police are taking DNA swabs of the letter containing racist abuse that was sent to Dyer, in the hope they can find those responsible.
Police Scotland told Sky Sports News on Tuesday: "All lines are being pursued. That would include any forensic opportunities."
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"Kilmarnock Football Club utterly condemns a letter which was delivered to the club this morning containing racist abuse directed at our manager, Alex Dyer," read a club statement on Monday evening.
"We are working with Police Scotland to identify any individuals involved in this disgusting act and we will pursue the strongest possible action we can against them.
"Racism in any form is completely unacceptable and must be called out whenever and wherever it is found.
"As a club, we have shown our support to rid the game and society as a whole of racial discrimination by taking the knee before each fixture this season and we will continue to do so."
Chief Inspector Nathan Calderwood, of Police Scotland, added: "We have been made aware of an offensive communication and enquiries into the matter are ongoing."
Dyer, who has been in charge at Rugby Park for a year, has received support from fellow managers in the Scottish Premiership.
Celtic boss Neil Lennon said the incident was "shocking" and that Dyer is one of the best football men he knows.
Motherwell manager Stephen Robinson labelled those who sent the letter "mindless idiots".
Livingston's late winner on Saturday made it five defeats in a row for Kilmarnock and eight losses in nine league games.
Eighth-placed Kilmarnock's next game on Wednesday is away to Motherwell, who are below them in the table on goal difference.
Dyer: No problem if board sack me
Dyer believes he maintains the support of the Kilmarnock board after a fifth straight defeat, but will have no problem if the club decides his time is up.
Scott Robinson's stoppage-time volley was caught up in storm-force winds and looped over Danny Rogers and under the bar to steal a 2-1 victory for Livingston at Rugby Park.
When asked if he thought he had the board's support, Dyer said: "Of course I have. I've got no problem.
"The board are a good board. If they turn around tomorrow and say it's time, I will shake their hands and I will move on, it's not a problem. There will be no animosity, there will be no hatred, because they have always been good to me since I have come here.
"So it's not a problem. I know where I'm from and I know what I've got and I'm lucky enough to be at a good football club with good people. So it's not a problem."