Deputies made the bust after observing two motorists racing down 6th Street, west of Etiwanda Avenue, around 12:30 a.m., sheriff's officials said.
From a distance, while waiting for additional units to crack down on the illegal event, deputies saw two more races.
Deputy Nicholas Clark said more than 27 people were arrested for the misdemeanor violation of participating in or abetting an illegal street race. The San Bernardino Sheriff's Department also impounded a total of 17 cars that were lined up for the event, some to race and some to watch.
The suspects, most from Riverside, Norco, Banning or Beaumont, were booked into the West Valley Detention Center with the exception of a juvenile female, who was was released to her parents at the Rancho Cucamonga Station.
Many of the vehicles towed were found to have illegal engines or transmissions. Sancat investigators are conducting a further investigation.
