OAKLAND -- Oakland Unified School District is buying all employees identity theft protection after five initially reported that their identities or financial accounts had been compromised, said school district officials.

"We want to err on the side of trying to make amends for this incident," said district spokesman Troy Flint. "We apologize to the community."

The preliminary cost estimate for the protection is $150,000 for two years of coverage and benefits from Identity Fraud, Inc. for present and past employees.

More employees have come forward, saying they also might have been affected, Flint said. Common reports are that thieves have used employees' names to order credit cards or for tax IDs. The district has a third party investigating the claims.

Unsecured documents were left in a former administration building at 1025 Second Ave. in Oakland that the district vacated after a flood in January 2013. The building was deemed unfit for further use.

Eighty years' worth of files stayed at the site, despite the district's efforts to transport the paperwork and equipment. Their removal progressed slowly.

"Nobody really knew what was there, where it was hidden, or to whom it belonged," Flint said.

It was a challenge determining how to categorize the paperwork, whether to digitize or shred it. Site access has also been an issue because of environmental hazards, he said.

The district took security measures to protect the property. Still, trespassers continued to break in by cutting locks, clipping fencing and busting through doors.

Last month, numerous buildings and grounds employees found files with employee Social Security numbers.

"There's no good excuse for why the paperwork remained there," Flint said. "It should have been moved to a secure location."

The district has most of the files out of the building. The remaining is set to be transferred by Friday.

Student records were not compromised.

"It is a matter we take seriously even though we obviously failed in this instance, which is inspiring us to make changes," Flint said.