The Spain international left the Basque side for Bavaria on a five-year deal earlier this summer, but his previous club are not amused with the German outfit's behaviour
The midfielder underwent a medical with the Germans without permission from his club, before completing his move the following day, and the Basque side are not amused with die Roten's behaviour.
"We are looking into the possibilities of taking legal action against Bayern Munich," Urrutia stated at a press conference.
"Javi Martinez had a valid contract with us, which was specifically protected by the rules and regulations of world football's governing body, Fifa."
Bayern Munich eventually met the player's €40 million buy-out clause to lure the Spain international away from Bilbao and the 24-year-old made his official Bayern debut at the weekend in the 6-1 Bundesliga win over Stuttgart.