Four small bombs exploded Sunday at industrial sites in the Basque region in a string of attacks that appeared to have been staged by the armed separatist group ETA, Basque police said. Two policemen and a security guard suffered minor injuries after inhaling toxic fumes at a chemical plant where one of the pre-dawn blasts occurred, police said. The explosions came a day after Spain's ruling Socialist party said it is seeking other parties' support for a parliamentary motion supporting the start of talks with ETA if the group renounces violence, although the negotiations would rule out concessions toward ETA's goal of Basque independence. If ETA involvement is confirmed in Sunday's blasts, it would be an embarrassment for Prime Minister Jose Luis Rodriguez Zapatero.The bombs exploded in four towns in Guipuzcoa province, the capital of which is San Sebastian. The injuries occurred in Bergara, where the bomb targeted a chemical plant whose products include a powerful acid for industrial use, an official at the Spanish Interior Ministry office in San Sebastian said. An undetermined amount of acid leaked into a river, she said.