DUBAI, United Arab Emirates — The Emirates detained a member of the country’s ruling family as prosecutors launched an investigation into allegations the sheik tortured another man, the country’s official news agency reported Monday.

If the case of Sheik Issa bin Zayed Al Nahyan goes to trial, it would be the first time in the oil-rich Gulf federation of seven semi-independent sheikdoms that a member of the ruling family faced criminal charges in a court of law.

Torture allegations against Issa first surfaced a year ago when his former business associate, Texas businessman Bassam Nabulsi, filed a lawsuit in the United States suing the sheik for millions of dollars he claimed he was owed for various business deals.

Nabulsi submitted video tapes, which the sheik had allegedly entrusted to him along with financial records and investment documents, to a U.S. federal court in Houston, saying the footage depicts torture committed by Issa.

In his suit, Nabulsi also charged Issa and other members of the ruling family with false imprisonment and with torturing him in an attempt to get the tapes back after Nabulsi’s business relationship with Issa soured.

At the time, Nabulsi’s lawyers showed The Associated Press still images from one of three videos, which appeared to show the sheik sodomizing a man with a cattle prod, beating him with a wooden plank and firing an automatic weapon into the sand around him.

Some parts of the videos have since aired on television stations and appeared on the Internet. They also show a man in police uniform holding the victim down during the abuse.

The Judicial Department in the Emirati capital, Abu Dhabi, said in a statement Monday it has referred “all documents, related to the recently broadcast video, depicting the ill-treatment of an individual to the Abu Dhabi Public Prosecution Office.”

The official statement, carried by WAM, said Issa was banned from leaving the country and that others suspected of involvement in the case also face detention.

The report did not say where Issa is held or name any of the other suspects. Emirati officials refused to comment due to the sensitivity of the case.

Nabulsi’s Houston-based lawyer dismissed the Emirates’ announcement of Issa’s detention and the launch of the investigation against the sheik as “a farce,” saying he doubted the case would come to trial.

Anthony Buzbee told The AP that he had offered to share with Abu Dhabi judicial authorities the testimony of three witnesses to the sheik’s brutalities and more than two hours of video footage showing Issa torturing 25 people, but never heard back from any official.

“They claim to do a comprehensive investigation, but the truth is they have not done so and I don’t expect them to,” Buzbee said, speaking on the phone from the U.S. “Sheik Issa will never be prosecuted and the whole is a farce and a joke.”

Although most members of the ruling Al Nahyan family hold the presidency and key positions in the government, Issa _ a half brother of the UAE’s president and a brother of the crown price _ has no official role.