Officers pulled over a vehicle at Wauchula Way and Sleepy Hollow Avenue shortly after 10:30 a.m. Sunday.
The encounter led authorities to a home in a residential area on the west side of Hayward, but Lt. Bernie Licata said police are not releasing details of the traffic stop because it would compromise the investigation. Officers who responded to the home in the 27600 block of Barcelona Avenue smelled a chemical odor.
Licata said a state Bureau of Narcotics Enforcement clandestine lab team responded to the home to dismantle the lab, and the Police Department's street narcotics team executed a search warrant.
Officers found two homemade explosive devices, Licata said.
An Alameda County Sheriff's Office bomb squad was called out to the home to dispose of the devices. The Hayward Fire Department also responded to ensure neighbors' safety.
Licata said seven people were arrested, including four Hayward men, one Hayward woman, one San Lorenzo man and one Newark woman.
The suspects were arrested on suspicion of being under the influence of a controlled substance, Licata said. The investigation is ongoing.