( CNN ) -- Arsonists attacked the administrative offices of leading Israeli football club Beitar Jerusalem on Friday , police said . The attack occurred just days after the club signed two Muslim players . No one was injured in the fire , which was discovered around 5 a.m. , police said . But the blaze damaged the club 's trophy room . Last Thursday , four club supporters were arrested on charges of making racist chants , apparently directed at the Beitar 's newest players , Zaur Sadaev and Dzhabrail Kadaev . They came from Russian League club Terek Grozny , based in Chechnya . On the same day they were signed , January 26 , fans at a Beitar match waved a banner reading `` Beitar -- pure forever '' and chanted anti-Arab slogans . Four were arrested . The Israeli Football Association later fined Beitar $ 15,000 and ordered the club to close the area at the Teddy Kollek Stadium where the club 's hardcore supporters usually gather . Meanwhile , investigators continue to figure out who is behind the arson attack . `` A thorough investigation has been opened by a Special Investigations Unit searching for suspects that fled the scene , '' police spokesman Micky Rosenfeld said . Israeli Prime Minister Benjamin Netanyahu condemned the `` shameful '' arson attack in a statement issued Friday . `` We can not accept such racist behavior , '' he said . Beitar 's general manager , Itzik Kornfein , issued a defiant message , saying the club would stand by its signing of Sadaev and Kadaev . He said bringing them on was the `` right decision , '' despite the subsequent controversy . `` We will keep strong , '' he told CNN . `` The club wo n't change it 's mind because of these criminals , '' he said . `` But I want to emphasize that a minority of people have been causing these actions . Beitar and most of its fans are not racist . '' Rosenfeld said security will be stepped up ahead of Beitar 's home match Sunday in the Israeli League against Bnei Sachnin , an Arab-Israeli team . Beitar , owned by Russian-Israeli Arkady Gaydamak , was founded in 1948 . The club 's crest features the menorah , which is also embedded in the emblem of the state of Israel . Throughout the club 's history many of their fans have remained implacably opposed to the signing of Arab or Muslim players .
Beitar Jerusalem offices are set on fire days after it signed Muslim players . Football club supporters are arrested for making racist remarks . Fans wave a banner at a match that says `` Beitar -- pure forever '' No one was injured in the fire , police say .