A motorcyclist was killed Sunday afternoon in a crash on Highway 101 in Summerland that caused a major traffic tie-up, according to the California Highway Patrol.

The wreck occurred shortly before 1 p.m. in the southbound lanes just east of Evans Avenue, the CHP said.

Witnesses told investigators the motorcyclist was in the right-hand lane, traveling about 55 mph, when he “appeared to pass out and slump over his motorcycle,” according to CHP Officer Jonathan Gutierrez.

He said the man then drifted across the left lane, struck the center-divider rail, and was ejected from the motorcycle.

The rider, a 53-year-old Newhall man whose name was not released pending notification of relatives, was declared dead at the scene, according to Carpinteria-Summerland Fire Department Battalion Chief Robert Kovach.

“At this point in the investigation, no drugs or alcohol are suspected in the cause of the collision,” Gutierrez said.

Two hours after the crash, the left lane remained closed while emergency responders on scene waited for Santa Barbara County Coroner’s Office personnel to arrive, the CHP said.

All lanes were reported open at 3:07 p.m.

The closure caused heavy congestion for southbound freeway traffic, which was backed up almost to Las Positas Road in Santa Barbara.

Surface streets through Montecito also were at a standstill as motorists tried to bypass the traffic jam.

The crash remained under investigation by the CHP.

Noozhawk executive editor Tom Bolton can be reached at tbolton@noozhawk.com. Follow Noozhawk on Twitter: @noozhawk, @NoozhawkNews and @NoozhawkBiz. Connect with Noozhawk on Facebook.

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Tom Bolton, Noozhawk Executive Editor

Noozhawk executive editor Tom Bolton can be reached at tbolton@noozhawk.com.