The government denied assertions that Lori Berenson, the American serving a 20-year sentence for aiding a leftist rebel group, was mistreated while being transferred to another prison last week. But her lawyer said he would broaden a complaint he had filed to include an accusation of sexual abuse. Her father, Mark Berenson, has also said she was molested. The justice ministry said that it ''denies the 'grave injury' her lawyers have denounced'' and that Ms. Berenson, 32, is ''in good health.'' Ms. Berenson's lawyer, José Luís Sandoval, said she was beaten and sprayed with tear gas by the police when she and another prisoner were taken from their cells last Friday. He also said Ms. Berenson had been fondled by a police officer. The justice ministry said that the transfer had been carried out according to regulations and that tear gas had been used when prisoners resisted the police.