UPDATE: 2:35 p.m. EST:
Initial news reports indicated that the Boeing 737-800 made an emergency landing, but Bobbie Egan, a spokesperson for Alaska Airlines, told HuffPost that no emergency was declared and that passengers did not exit the aircraft using the emergency exits.
The plane, which had 126 passengers and six crew members, has been inspected and cleared by the Transportation Security Administration and by the Alameda County Sheriff's Department.
"We take these kinds of threats very seriously," Egan told HuffPost. "We did due diligence in making sure that the aircraft was screened and cooperated with local law enforcement.
According to a tweet from KCBS, the bomb threat was made with a note at San Francisco airport. KCBS also reports that the two passengers were removed in handcuffs.
KIRO-TV reports that images from a news helicopter show that K-9 units are inspecting the baggage on the tarmac.
The flight was en route from Seattle to Oakland and scheduled to land at 8:13 a.m., KIRO-TV reports. It landed at 7:50.
UPDATE: 1:20 p.m. EDT:
Alaska Airlines spokeswoman Bobbie Egan says that no bomb was found on the plane, and baggage is going through additional security screening.
This is a developing story. Check back for updates.
WATCH: Raw video from CBS San Francisco: