Police were staking out a hillside in Sha Tin last night in the hope of arresting three suspected illegal immigrants. The men, who were armed with knives, were first spotted climbing into a hostel under renovation near Pau Tau Village at about 9.30am. Suspecting the men were robbers, two decoration workers alerted police. The three suspects fled before they could be arrested, then eluded a four-hour air and land search involving about 130 officers and two police dogs. Police said no property had been stolen.