Police are searching for two men and a woman in connection with the explosion of a hand grenade detonator yesterday outside the busy Dionysos restaurant at the foot of the Acropolis. Restaurant customers saw two men, one covered in blood, and a woman, all of whom had been sitting at a table outside the restaurant, run away after the blast, which rocked the area, startling customers and tourists near the ancient monument. The men drove away on a motorcycle parked outside, while the woman fled on foot in another direction. A large police contingent cordoned off the area after the blast. Initial investigations indicated the explosion had been caused by the detonator of a hand grenade, of Eastern European (probably Russian) origin. Police believe the individuals concerned may be common criminal members of a protection racket. But they are investigating all possibilities. Hospitals and medical centers are being searched for suspects, and analyses of the bloodstains found at the scene are also being made. No one else was reported injured in the explosion.