Absences among transportation security workers this weekend reached their highest since a partial government shutdown began five weeks ago, the Department of Homeland Security said on Sunday, while immigration enforcement agents prepared to fill in for them at some of the busiest U.S. airports.

At airports in Houston, New York and Atlanta, more than one-third of Transportation Security Administration staff were calling in sick or otherwise absent, the department said, as the shutdown left tens of thousands working ?without pay while congressional Democrats and Republicans argue over the department¡¯s budget. To help fill the staffing gaps, hundreds of Immigration and Customs Enforcement agents will deploy to airports ?starting on Monday, ?government officials have said.

The department said on Sunday it would not publicly share details about the ICE deployment, in order to preserve ?operational security, but sources briefed on the matter said the current plan calls for deploying agents to 14 locations, although that figure may change. For now, ICE personnel will not be deployed in areas behind airport security checkpoints because they lack the specific clearance needed, the sources said.