Four men, including a police officer and police special guard, were arrested early yesterday morning on the grounds of the former royal estate in Tatoi where they were allegedly digging for hidden treasure. Police are looking for one more officer who managed to escape. The two policemen and the special guard all serve at the Tatoi police station, which is responsible for guarding the estate north of Athens. The suspects were caught as they were digging a hole some 3.5 meters deep, apparently looking for gold coins. Officers had been tipped off about the case two months ago, sources said, and had been tailing the suspects. Police found metal detectors, a gun and digging equipment during their raid yesterday. Sources said that the area would now be closely guarded as police fear that other treasure hunters may be tempted to continue the search.