Under the shadow of a raised terror alert surrounding the conference in Annapolis, police have arrested 2,500 Palestinians working illegally in Israel over the last two days. The police said the crackdown was designed to reduce the threat of terror attacks launched by terrorists seeking to derail the conference. The 2,500 were detained and removed to the Palestinian Authority, and approximately 60 criminal files were opened against employers, smugglers and those providing shelter to the workers. The operation was under way for two days, and approximately 2,000 police officers and Border Police participated. Police explained that terrorists often infiltrate along the same routes as illegal workers who make their way across the Green Line every day. Officers in the National Headquarters said that the level of alert would continue at least until Thursday, with increased police presence in public gathering areas and at the entrances of major cities. But although long lines of traffic were reported at checkpoints following more stringent checks of vehicles, the first day of the Annapolis summit was completed with minimal interference by terror operatives in the West Bank . A suspicious package was discovered at Mishtara Habritit Junction on Route 60, and items believed to be planted in advance of a potential attack were discovered in Kiryat Sefer, near Modi'in. In addition, two incidents of rock-throwing by Palestinians were reported, one north of Hebron and one south of the Judean city. The windshield of one vehicle was damaged, but no injuries were reported. The Judea and Samaria District Police refused to comment Tuesday on the overall security picture in their district, but did say that in the coming days, a report would be published regarding attacks and vandalism against what they described as "national infrastructures."