WOODSTOCK, Ill. (AP) — Congressmen and senators from Illinois are urging a review of health policies after a mumps outbreak at a northern Illinois county jail that houses immigrant detainees.

Health officials confirmed six mumps cases earlier this month at McHenry County Jail, which contracts space to U.S. Immigration and Customs Enforcement.

In a Wednesday letter the Democrats cite “serious concern” about conditions and urge a “thorough and urgent” policy review. The group seeks details on the outbreak.

They are U.S. Reps. Jesus Garcia and Lauren Underwood and U.S. Sens. Dick Durbin and Tammy Duckworth.

ICE officials say each detainee receives a medical examination upon arrival at the facility.

Immigration and health officials have previously said the infected detainees were isolated and those exposed were quarantined.

Mumps is a contagious virus causing swollen glands, puffy cheeks, fever and, potentially, hearing loss and meningitis.