TALLINN, January 20 (RIA Novosti, Nikolai Adashkevich) - Estonian President Arnold Ruutel said he was shocked to find out that his underage granddaughters were throwing parties in the presidential palace in his absence, a local newspaper said.

"I am deeply concerned and I apologize once again for the incidents on behalf of my family," Ruutel, currently on a visit in the United States, said in an interview with the newspaper Postimees. "When I delivered my New Year address to the nation, I expressed concerns over problems with youth, but I did not suspect that these problems could hit my own family so hard."

Ruutel said he was confident that outsiders could not have seen secret documents in the presidential chancellery.

"According to the rules, a document is returned to the official responsible for it immediately after it has been examined and cannot fall into the hands of an outsider," Ruutel said.

The president said that, shortly upon his return home, he would be given a report by the interior minister, talk to his granddaughters and then appear in public with an explanation.

The Estonian television program Pealtnagija said Thursday that the president's granddaughters, Helena, 15, and Maria, 13, who live with their grandfather, had organized parties in his absence for their friends in the president's residence in the Kadriorg Palace.

The program showed photos taken during the parties and comments from some of the partygoers.

According to the program, the young people who gathered in the presidential residence drank alcohol and walked around the offices containing secret documents.

Interior Minister Kalle Laanet has ordered an investigation into the work of palace guards.