U.S. lawmakers have abandoned privately funded trips to Turkey after a congressional investigation found misconduct in previous trips, a report said Wednesday.

No member of Congress "has accepted a privately sponsored trip to Turkey since May 2015, with the exception of one congressman who made an August trip sponsored by a Norwegian group," according to an article by the USA Today newspaper.

Last year, an ethics investigation into lawmakers' trips to Turkey found misconduct by sponsors linked to the Gülen Movement, a secretive religious group led by U.S.-based Turkish preacher Fethullah Gülen.

The probe by the Office of Congressional Ethics revealed that Gülen-linked organizations were hiding the true source of funding for nearly 200 trips.

According to the data the daily collected, the number of privately funded trips to Turkey in 2010 fell to just 100 by the second half of 2015.

But U.S. government-sponsored trips reported by Congress fell slightly from 110 in 2013 to 92 in 2015. The Gülen Movement runs a network of schools and commercial enterprises in Turkey and around the world.

Besides the congressional probe, an FBI investigation into charter schools linked to the group stemming from accusations of financial corruption, may have triggered lawmakers' unwillingness to the Gülen-sponsored trips.

A row between the movement and the Turkish government erupted in 2013 after a failed attempt by the group to form a quasi-state via a clandestine group of Turkish bureaucrats and senior officials. Since then, Gülen-linked organizations have lobbied against Ankara in Washington.

The Turkish National Security Council in late 2014 classified the group as a terrorist organization for creating an illegal structure embedded in the country's institutions, including the judiciary and the police, in an attempt to overthrow the government.

Referred to as the Gülenist Terror Organization (FETÖ), the movement is seen as a threat to Turkey's national security. It has been accused of infiltrating state institutions in Turkey and attempting to overthrow the government. Government officials have continuously expressed their determination to continue to lawfully fight the Gülen Movement, whose followers are accused of infiltrating state institutions to gain control of state mechanisms, illegal wiretapping, forgery of official documents and espionage.