SUNNYVALE -- A 29-year-old Sunnyvale man has been tentatively identified as the man fatally struck by several cars on a dark stretch of northbound U.S. Highway 101 in Sunnyvale Monday morning, according to the California Highway Patrol.

The man was unrecognizable when retrieved from the highway and Santa Clara County coroner's officials are working to positively identify him, CHP Officer Todd Thibodeau said.

Sound walls block access to the freeway, so investigators believe the man walked up an onramp to enter the freeway, according to Thibodeau. The man was spotted by motorists at about 1:50 a.m., he said.

Drivers reported seeing the man walking along the shoulder before he suddenly darted across lanes just north of Lawrence Expressway. He was first struck in the No. 2 lane by a man driving a Honda Passport, which came to rest in the No. 3 lane following the collision, Thibodeau said.

About two minutes later, a Nissan Altima struck the Honda Passport, pushing the Altima into the sound wall and the Passport into the No. 4 lane. A Honda Civic then struck the Passport, pushing it to the side of the freeway, Thibodeau said.

All three drivers were transported to local hospitals with minor injuries, according to Thibodeau.

During the pileup, numerous cars struck the pedestrian.

Officers received reports of the pileup at about 2 a.m., and believe the man was initially struck at about 1:55 a.m., Thibodeau said.

The area in which the man was hit does not have roadside lighting, so drivers rely on ambient light and headlights in the dark, Thibodeau said.

Officers have not determine why the man entered onto the highway, and will continue the investigation and wait for a toxicology screen on the victim to determine if he was under the influence of alcohol or drugs, Thibodeau said. He does not appear to have been a transient.

All northbound lanes of the highway were shut down while officers investigated the accident this morning.

A Sig-alert was issued at 2:11 a.m. The No. 1 and 2 northbound lanes were reopened at about 6:30 a.m., and the No. 3 and No. 4 lanes were cleared by 7:45 a.m., according to the CHP.