PORTLAND — The Portland and South Portland police and fire departments, Cumberland County and state emergency agencies, the Coast Guard and private agencies will participate in a mock emergency drill at the Portland International Jetport on Saturday.

Local traffic will be affected by the drill for much of the day.

The agencies will carry out search and rescue operations during the exercise, which is required by the Federal Aviation Administration. It’s designed to test the jetport’s ability to respond to an aircraft emergency.

The drill’s scenario involves a plane bound for the jetport crashing into the Fore River just south of the Veterans Memorial Bridge. Northbound lanes of the Veterans Memorial Bridge from South Portland to the Fore River Parkway will be closed to all traffic from 9 a.m. to 3 p.m.