Ralston Purina, the nation’s largest manufacturer of animal feed, announced it is freezing all donations from a coupon drive to benefit the City of Hope National Medical Center in Duarte.

Company officials said the suspension will last until a National Institutes of Health investigation of the animal research center is completed. The institutes suspended about $5 million in

research funds Aug. 1 until an investigation of guideline violations at the research facility is completed. On Aug. 8, Purina ran a coupon drive in The Times to raise funds for the City of

Hope. The company received many phone calls from irate animal rights activists, said a spokeswoman for People for the Ethical Treatment of Animals, a national animal rights organization.