WASHINGTON (CNN) -- Records from a cell phone used by President-elect Obama were improperly breached, apparently by employees of the cell phone company, Verizon Wireless said Thursday.

An Obama spokesman said the transition team was told Verizon Wireless workers looked through billing records.

"This week we learned that a number of Verizon Wireless employees have, without authorization, accessed and viewed President-Elect Barack Obama's personal cell phone account," Lowell McAdam, Verizon Wireless president and CEO, said in a statement.

"All employees who have accessed the account -- whether authorized or not --- have been put on immediate leave, with pay."

The Obama transition team was notified Wednesday by Verizon of the breach, said team spokesman Robert Gibbs. He said the president-elect no longer uses the phone.

McAdam said the device on the account was a simple voice flip-phone, not a BlackBerry or other smartphone designed for e-mail or other data services, so none of Obama's e-mail could have been accessed.

Verizon Wireless, meanwhile, has launched an internal probe to determine whether Obama's information was simply shared among employees or whether "the information of our customer had in any way been compromised outside our company, and this investigation continues," McAdam said in an internal company e-mail obtained by CNN.

"Employees with legitimate business needs for access will be returned to their positions, while employees who have accessed the account improperly and without legitimate business justification will face appropriate disciplinary action," McAdam said, "up to and including termination."

The company has alerted "the appropriate federal law enforcement authorities," McAdam said.

Gibbs said that while the Secret Service has been notified, he is not aware of any criminal investigation. He said he believes it was billing records that were accessed.

Gibbs said that anyone viewing the records likely would have been able to see phone numbers and the frequency of calls Obama made, but that "nobody was monitoring voicemail or anything like that."

CNN White House correspondent Ed Henry contributed to this report.

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