TERRE HAUTE, Ind. -- A fire that destroyed Hillary Rodham Clinton's Terre Haute presidential campaign office early Friday was accidental, officials said.

Investigators haven't determined the cause, but foul play has been ruled out and a wiring problem could be to blame, officials said late Friday afternoon.

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Slideshow: Fire Scene

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Two people were inside when the fire started just after midnight. but escaped without injuries, said Terre Haute Fire Department spokesman John Gardner.

Former President Bill Clinton stopped briefly outside the burned Weststaf building on Thurs Street Friday on his way to a campaign speech in the small city of Clinton about 20 miles north of Terre Haute.

"Our young workers here are undeterred, and they're ready to roll so we'll get it going," he said.

Clinton laughed when asked whether the fire was a bad sign for his wife's campaign. "No, I think this is a good omen," he said. "We'll rise from the ashes like the Phoenix."

A volunteer firefighter driving past the building spotted flames on the roof warned two women inside, officials said.

"They got out and a few seconds later the ceiling fell in where they were working and about five minutes later it was fully engulfed in the roof," Gardner said.

The roof of the one-story building partially collapsed and a part of the front wall collapsed on a parked car, which then caught on fire. The adjoining office of a staffing services agency had water and smoke damage, but a firewall held back the flames, Gardner said.

Donna Gibbons, a Clinton campaign worker, said some campaign materials -- items such as pamphlets -- were lost in the fire.

Campaign officials said they were trying to determine whether the fire destroyed information such as the names, addresses and phone numbers of local Clinton supporters. The campaign would use that information to remind them to vote in the May 6 primary.

Hillary Clinton, a U.S. senator from New York, and U.S. Sen. Barack Obama, D- Illinois, are locked in a tight race for the Democratic presidential nomination. Both candidates have set up offices throughout Indiana as they vie for the state's 72 delegates in the May 6 primary.

Bill Clinton spoke Thursday night in nearby Vincennes. Obama was to speak Friday night at Terre Haute North High School.