A pedestrian was struck and killed early Tuesday, forcing the closure of all southbound lanes of southbound Highway 101 in Sausalito at the Spencer Avenue off-ramp, according to the California Highway Patrol.

The CHP said officers responded to reports just before 4:30 a.m. of a pedestrian walking on the highway.

A Sig-alert was issued at 4:52 a.m., closing all southbound lanes — without providing an estimate of when they will reopen — and the Marin County Coroner’s Office responded to the scene, the CHP said.