The United Nations Organization stopped cooperating with two Russian airlines on the ground that some of the companies’ employees are suspected to be involved in legal offenses of sexual nature, Reuter reports.

An anonymous representative of the United Nations Department of Peace-Keeping Operations (DPKO) said to reporters off the record that the offense in question was really grave, but no further explanations were given.

The DPKO representative Kieran Dwyer did confirm that the charges involved a few employees of UTair Airlines and Nefteyugansk United Airline Transportation Company that both have contracts with the UN missions in Congo and Sudan, RIA Novosti reports.

‘We understand what incident is involved here. The United Nations have taken the necessary measures,’ Dwyer said.

‘Our investigation has led us to a conclusion that some of the charges involving a number of employees are actually grounded. Our cooperation with the two airlines has been halted, and the employees involved in the incident under investigation have been fired and restrained from taking part in any other UN missions,’ the DPKO representative added.