A truck that was transporting research monkeys crashed. Police say they carried dangerous diseases, claims that have since been refuted.

Officials are still struggling to recapture monkeys that escaped a research facility in Yemassee, South Carolina, last week — and have even made efforts to contact monkeys still inside, officials say.

Conditions at primate-research centers often drive monkeys to the point of madness. Last year’s news-making escape has ...