Davao City Mayor Baste Duterte is being urged by Senator Erwin Tulfo to investigate his own chief of staff and the city’s contracts with GenCorp Industries Inc., a company allegedly linked to his sister, Vice President Sara Duterte. The mayor previously claimed he had no direct involvement in the GenCorp deals, prompting criticism from prosecution spokesman Zia Alonto Adiong, who questioned how a head of procurement could be unaware of companies winning government contracts.