Suspicious events are once again happening at the Dallas Zoo as officials say two of the zoo’s emperor tamarin monkeys were missing in what appears to be an intentional act.

The zoo tweeted its animal care team discovered two of its emperor tamarin monkeys were missing Monday morning.

Zoo officials said the monkeys would likely stay close to home, but staff searched near the habitat, as well as the rest of the zoo, and could not find them.

The incident has now become an active Dallas Police Department investigation. Dallas police said in a statement to USA TODAY a preliminary investigation determined someone intentionally cut into the monkey enclosure. 

“It was clear the habitat had been intentionally compromised,” the zoo said. “Based on the Dallas Police Department’s initial assessment, they have reason to believe the tamarins were taken.”

The zoo had been closed Monday due to inclement weather and was scheduled to be closed Tuesday and Wednesday.