(Releads with police statement) By Vincent Fribault GENEVA, May 24 (Reuters) - Police said an early morning fire that destroyed Geneva's largest synagogue on Thursday, a Jewish holiday, may have been arson but they did not rule out an accidental blaze. The 1970s building was empty at the time, though it had hosted an event attended by 200 people the previous evening. No one was injured, police said in a statement. "We are not ruling anything out, a possible simple technical problem or a deliberate act," spokesman Eric Grandjean said. Earlier, another police spokesman, Philippe Cosandey, said a "deliberate act" was suspected as the fire spread extensively within minutes. The building's entrance was blackened with soot and windows were shattered by the force of the blaze, which was extinguished around 0615 local time (0415 GMT) after some 40 firefighters waged a two-hour battle, the statement said. The prayer-room part of the synagogue was damaged by smoke and water. Some regular worshippers, who are mainly Sephardic, gathered near the building to sing prayers. Nessim Gaon, chairman of the Jewish centre for culture and religion in Geneva, said he believed the act was deliberate. "The destruction to the interior is huge," Gaon, one of the founders of the Hekhal Haness synagogue and founder of a Geneva-based commodity trading empire, told Reuters TV at the scene. "The origins of this must be deliberate." The fire took place during the Jewish holiday of Shavuot, which marks the giving of the Torah, the Jewish holy book, by God to Moses on Mount Sinai over 3,000 years ago. Police said it was too early to determine whether the attack could have been racially motivated but that they had reinforced surveillance around other synagogues in the lakeside city. Wealthy Switzerland is known for public order and tolerance but has become increasingly the focus of religious tension, particularly targeting its Muslim minority. Anti-Semitic acts that become public are rare, but in June 2001 an Israeli rabbi was shot dead on the streets of Zurich. (Additional reporting by Thomas Atkins in Zurich and Stephanie Nebehay in Geneva)