In the letter the DTP mayors said their constituents did not want the channel to be shut down, adding that a strong tool for improving Turkey's democracy and human rights situation would be removed if it were to be closed.
The office will decide whether to file charges against the mayors based on the inquiry.
Among those who signed the letter were Diyarbakır Mayor Osman Baydemir, Batman Mayor Hüseyin Kalkan, Tunceli Mayor Songül Erol Abdil, Şırnak Mayor Ahmet Ertak and Hakkari Mayor Metin Tekçe.
Baydemir, who personally sent the letter to Denmark in the name of all the mayors, said they hoped Roj TV would be allowed to broadcast like any other station under the supervision of the Supreme Board of Radio and Television (RTÜK).
Turkey had appealed to Danish officials in early 2005 for the closure of Roj TV, claiming it was a mouthpiece of the outlawed Kurdistan Workers' Party (PKK). Denmark responded that Roj TV had not committed any crime under Danish law.
The Turkish Foreign Ministry lodged a formal complaint in Denmark in September calling for a criminal inquiry into Roj TV's conduct.
In November a Danish prosecutor initiated an inquiry into Roj TV to determine whether it had any financial links to the PKK.
On Nov. 15 Prime Minister Recep Tayyip Erdoğan refused to attend a joint press conference with his Danish counterpart because Roj TV correspondents were present.
© 2005 Dogan Daily News Inc. www.turkishdailynews.com.tr
The Diyarbakır Prosecutor's Office has opened a criminal inquiry into a letter signed by 56 Democratic Society Party (DTP) mayors and sent to Danish Prime Minister Anders Fogh Rasmussen, asking him not to close down Roj TV, which broadcasts in Kurdish from Denmark.