TRADE and Industry Secretary Manuel Roxas II has given cement makers until Friday to justify the recent increase in cement prices. andnbsp;Roxas warned that failure to come up with a valid reason for the price hike would force the Department of Trade and Industry (DTI) to withdraw the tariff shield against imports granted to the industry. andnbsp;andnbsp;The measure "puts the goodwill of cement firms to the test. It is not designed for them to engage in predatory pricing," Roxas said in a press briefing Monday. andnbsp;The DTI imposed last June a safeguard duty of 20.60 pesos (37 cents) per 40-kilogram bag of imported cement. This was in response to the urgent appeal of cement manufacturing firms, which claimed the entry of cheaper imported cement has been hurting the local industry.