Three Nigerians have been indicted in a federal cyber-fraud conspiracy that involved hacking into the computer files of a Minnesota company and obtaining personal data and W-2 tax information on 1,200 people, then using the data to file bogus tax returns.

The three defendants are believed to be in Nigeria, according to a statement issued Wednesday by U.S. Attorney Erica MacDonald in Minneapolis.

“We remain optimistic that the defendants will have their date in court in the U.S., but we can’t get into further detail with respect to our apprehension efforts,” said Tasha Zerna, a spokeswoman for the U.S. Attorney’s Office.

The defendants allegedly gained access to accounts maintained by a company that provides human resource and payroll services to numerous businesses, stealing W-2 data and personal identifying information such as Social Security numbers and dates of birth.

A law enforcement source, speaking on condition of anonymity, confirmed that the company was Ceridian, which has offices in Bloomington and describes itself as a global human capital management software company. Attempts Wednesday afternoon to reach representatives of the company were unsuccessful.

The stolen accounts were registered with a web-based program that allowed employees to download a copy of the W-2 IRS form from an internet portal. The defendants allegedly used purloined information to prepare and electronically file tax returns with the IRS, according to a news release by the U.S. Attorney’s Office.

The three defendants and unidentified others also gained unauthorized access to individuals’ accounts maintained by the U.S. Department of Education, which also contain tax information, and they allegedly used that information to file phony tax returns with the IRS.

They attempted to claim about $16.4 million in fraudulent tax funds, the U.S. Attorney’s Office said in a statement. “The exact actual loss would be established at trial,” Zerna said.

Named in the indictments were Olufemi Oluwaseun Banjo, also known as Femi Banjo, 37; Francis Nwabueze Iwuoha, 38; and Oluwadamilare Gbenga Macaulay, 32. They are charged with wire fraud, aggravated identity theft and conspiracy.

The investigation was conducted by the IRS’ criminal investigation division, the U.S. Department of Education, the Office of the Inspector General, and the FBI. Assistant U.S. Attorneys Julie Allyn and Angela Munoz-Kaphing are prosecuting the cases.

Staff writer Paul Walsh contributed to this report.