By ABDULLAH AL-SHIHRI and AYA BATRAWYRIYADH, Saudi Arabia (AP) a¿¿ Garbage is piling up on streets around the mosque housing the burial site of the Prophet Muhammad. Grocery stores have shut their doors and almost half of Saudi Arabia's small construction firms have stopped working on projects. The mess is because foreign workers on which many businesses rely are fleeing, have gone into hiding or are under arrest amid a crackdown launched Nov. 4 targeting the kingdom's 9 million migrant laborers. Decades of lax immigration enforcement allowed migrants to take low-wage manual, clerical and service jobs that the kingdom's own citizens shunned for better paying, more comfortable work. Now, authorities say booting out migrant workers will open more jobs for citizens, at a time when unemployment among Saudis is running at 12.1 percent as of the end of last year, according to the International Monetary Fund. But the nationalist fervor driving the crackdown risks making migrant workers vulnerable to vigilante attacks by Saudis fed up with the seemingly endless stream of foreigners in their country. The majority of workers hail from India, Pakistan, Bangladesh, Indonesia and the Philippines, as well as Egypt and Yemen. Others, mostly from east Africa, have never acquired visas, often taking perilous boat journeys across the Gulf of Aden to Yemen from where they cross illegally into the kingdom with the help of smugglers. Since the Saudi government began issuing warnings earlier this year, hundreds of thousands of foreign workers have been deported, though some were able to avoid arrest by getting proper visas in an amnesty program. That amnesty ended last week, and some 33,000 people have since been placed behind bars. Others have gone into hiding. With fewer people to do the job, the state-backed Saudi Gazette reported that 20,000 schools are without janitors. Others are without school bus drivers. Garbage became so noticeable around the mosque housing the Prophet Muhammad's tomb that a top city official in Medina helped sweep the streets, the state-backed Arab News website reported.