SAN JOSE — Fire investigators are treating an early morning fire at a medical marijuana clinic in North San Jose as suspicious after detecting a strong odor of gasoline, according to a fire captain.

The small, one-alarm fire at 1670 Zanker Road was quickly contained this morning, helped in part by the activation of sprinklers inside the building, according to San Jose Fire Capt. Mike Van Elgort. The fire was contained to an office area inside the cannabis club, the Palliative Health Center, according to a company website.

Van Elgort said the building was locked and firefighters had to force their way into the building after arriving at 4:20 a.m. Firefighters detected a “strong odor of gasoline” inside the building, and the blaze was contained to a small office area which did not many potential sources for fire, Van Elgort said.

Van Elgort would not discuss what other suspicious items were located inside the building.

The origin and cause of the fire remains under investigation.

Ernie Arreola, a manager for the cannabis club, said someone broke into the building by breaking a window in a conference room. Arreloa said nothing was stolen; the cannabis club has internal security, including secondary doors with time locks that need passwords.

He said the business does have video surveillance cameras and that the footage will be given to the proper authorities.

Staff photographer Gary Reyes contributed to this report. Contact Mark Gomez at 408-920-5869. Follow him on Twitter @MarkMgomez