Thursday morning's inferno that crippled BART service between Oakland and San Francisco might have been intentionally set, according to investigators. Police are now asking the public for help in finding three suspicious people who were lingering around a West Oakland construction site just before the fire ignited.

The Chronicle reports:

Investigators from the Oakland Fire Department and the federal Bureau of Alcohol, Tobacco, Firearms and Explosives focused their attention on debris at the south entrance of the unfinished Red Star senior housing complex, where they believe the inferno started.

Lisa Baker, an Oakland battalion chief, said a security guard watching the four-story site at Seventh Street and Mandela Parkway had reported three suspicious people near the building shortly after 2 a.m. The fire broke out minutes later and grew to a three-alarm blaze within half an hour, Baker said.

"It went up like kindling," she said.

Furthermore, the blaze began just moments after a security guard for Command International Security Services "reported being harassed by three teenagers or young men who tried to attack him."

Yesterday's blaze caused damage to the BART rails in Oakland, and effectively ruined Thursday's commute for many people who travel across the Bay.