(CBS) — Chicago Public Schools officials have contacted the families of 4,000 students – because of a data breach involving personal information on those students.

Names of 4,000 students, plus their home addresses, phone numbers, disability status and student ID numbers: CPS Spokesman Bill McCaffrey says all that was mistakenly turned over to five software companies who are bidding to get a contract with the Chicago Public Schools.

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“We had provided them information so they could demonstrate to us how their software works in terms of planning out efficient bus routes.

“We should’ve provided random data to them, and unfortunately provided specific data, and that’s where the breach was.

“But all of the companies have assured us that this information has been destroyed. They’re all reputable companies.”

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And ironically, McCaffrey says he cannot reveal the names of the five companies because of the way the bidding process works.

McCaffrey says no Social Security numbers were released.

He says the breach was in March.

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He says CPS will be “providing training to make sure a breach of this nature does not happen again.”