QUETTA, Pakistan — A car bomb targeting a bus carrying Shi’ite Muslim pilgrims killed 19 people in southwest Pakistan on Sunday, officials and eyewitnesses said.

Earlier Sunday, 21 tribal police officers believed to have been kidnapped by the Taliban were found shot dead in Pakistan’s troubled northwest tribal region, government officials said. There were conflicting reports about whether the attack on the Shi’ites was carried out by a suicide bomber, or if the car bomb was detonated by remote control.