Brazilian officials on Sunday released three Cisco Systems officials, including its president for operations in Brazil, days after their arrests in a tax fraud investigation.

A fourth Cisco (Nasdaq: ). official remains in custody, according to media reports. That person has not been identified.

The four were arrested last week in the massive tax probe. In all, officials arrested more than 40 people and seized millions of dollars in equipment.

Cisco, which has a major operation in Research Triangle Park, confirmed in a statement on Sunday that Pedro Ripper, its country manager, had been released. The company also noted that no “formal charges” have been filed against its employees.

“We are gratified that three of our employees detained by the Brazilian authorities earlier this week have been released,” Cisco said in the statement posted on its Web site.

“No formal charges have been brought against our employees at this time, and we are doing all that we can to support them,” Cisco added. “Right now, our foremost concern is for our employees and their families as they focus on resuming with their lives. We look forward to Pedro Ripper returning to his role as country manager of Cisco Brazil as we continue to give our full attention to the business of working closely with our partners to support our loyal customers in Brazil, while cooperating with appropriate authorities.”

A slightly different statement was posted on Cisco’s Brazilian Web site, according to media reports.

"Cisco Systems communicates its satisfaction that three of its employees, held by Brazilian authorities since last week, were released,” it said. “No formal accusations were made against them until now, and the company is keeping up efforts to help them.”

The releases came after Cisco published a series of ads in Brazilian newspapers on Sunday in which the company denied that it had acted “inappropriately.”

Brazilian officials have released 23 of the 40 people that were arrested, according to The Associated Press, which cited Brazilian media reports.