SAN FRANCISCO (BCN) – A motorcyclist crashed and died Monday afternoon on the Bay Bridge, California Highway Patrol officials said. 

The crash was reported to the CHP at 1:45 p.m. just west of Treasure Island, CHP spokesman Officer Mark Andrews said. 

According to the CHP and the San Francisco medical examiner’s office, 58-year-old Alamo man Robert Peng was pronounced dead at 2:02 p.m. 

Andrews said the CHP doesn’t know yet why Peng crashed. No debris was on the road and no other vehicles were in the area, Andrews said. 

But for some reason, Peng lost control of the bike and suffered major injuries. Two traffic lanes were closed for about 90 minutes as CHP officers investigated the crash, Andrews said.