The Guru Maneyo Granth Gurdwara Sahib, located in Orangevale, about an hour from San Francisco, was inaugurated on January 12. It was vandalized with white nationalist graffiti, which included the phrase "White Power" and depicted a swastika on a concrete slab at the front entrance.
Along with the FBI, the Sacramento County Sheriff's Office were also actively investigating the incident.
Harbans Singh Sraon, a spokesman for the gurdwara, told the India-West newspaper that FBI detectives have consistently visited the facility since the "bias-motivated crime" occurred.
Sacramento Sheriff Deputy Lacey Nelson told India-West that detectives specifically assigned to investigate hate crimes have been actively investigating the incident since Monday morning.
Crime scene investigators have been collecting forensic evidence from the scene, and detectives have canvassed the neighbourhood, speaking to residents who may have observed the crime.
Detectives have obtained video footage from the neighbourhood, said Nelson, adding that the nature of evidence found in forensics and on video has yet been released.
"This is an ongoing investigation. We do take these types of cases very seriously," the Deputy added.
The gurdwara has also received support from the interfaith community.
Pastor Dave Ratcliff of the Sierra Presbyterian Church, said: "We stand with you and your congregation in rejecting all acts of violence and hatred. You are not alone."
The Council on American Islamic Relations also condemned the hate crime, saying "we must all stand up against hate in our communities".
"We are here to support the Sikh community and encourage any witnesses to come forward with information about this hate attack on a house of worship," it added.
The Sikh American Legal Defense and Education Fund noted the alarming rise in the number of hate crimes committed by white supremacist groups.
( With inputs from IANS )