Asserting that it was as much concerned about the pollution caused by motor vehicles in Delhi as the State Government, the Union Surface Transport Ministry today denied reports that it was holding up a proposal of the Delhi Government for conversion of buses from diesel to compressed natural gas(CNG).A statement from the Ministry said no proposal had been received from the Delhi Government and, therefore, the question of delay in approving it did not arise. It sought to clarify that the only proposal which it had received was from the Delhi Transport Corporation(DTC) directly on August 6 in respect of conversion of Leyland buses.