Authorities were working Sunday to recapture two chimpanzees that escaped from a sanctuary in eastern Missouri.

At least one of the two escaped chimps had been tranquilized by Sunday afternoon while the other one was contained within a perimeter set up by Jefferson County sheriff’s deputies and animal control personnel.

Sheriff’s office spokesman Grant Bissell said the plan was to tranquilize the chimps and then return them to the sanctuary that is about 35 miles (56.33 kilometers)  southwest of St. Louis near the town of Festus.

Bissell said one of these same chimpanzees escaped from the sanctuary just a few weeks ago.