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.
Strange events continue at Dallas Zoo
The missing monkeys is just one of several unusual events that have taken place at the zoo in recent weeks.
On Jan. 13, the zoo was shut down after Nova, a 4-year-old clouded leopard, went missing. She was later found on zoo grounds and safely secured. Harrison Edell, executive vice president of animal care and conservation at the Dallas Zoo, noted there was a tear in the mesh of Nova's enclosure that morning.
On Jan. 14, Dallas police opened a criminal probe and found that an intentional cut was made on the enclosures that house langur monkeys. None of the monkeys were missing or harmed.
On Jan. 21, Pin, a 35-year-old endangered adult lappet-faced vulture, was found dead in its habitat. The zoo said a veterinary team trying to determine the cause of Pin's death found "an unusual wound and injuries, which pointed to this not being a natural death."
More: An Illinois family heard a noise in their garage. It was an endangered ring-tailed lemur.
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Police investigate zoo incidents
Dallas police previously told USA TODAY officers were investigating whether any of the prior incidents were related. The zoo said it plans to offer a $10,000 reward for information leading to an arrest and indictment the vulture's death.
The zoo said on Jan. 22 it would be increasing security measures, including adding additional cameras throughout the park and increased security patrols.
"We will continue to implement and expand our safety and security measures to whatever level necessary to keep our animals and staff safe," the zoo said.
What to know about emperor tamarin monkeys
Emperor tamarin monkeys are small monkeys with "long, white whiskers that sweep back from the muzzle on both sides and look like mustaches," according to the Smithsonian's National Zoo and Conservation Biology Institute. The monkeys are believed to get their name from German emperor Wilhelm II, who had a mustache.
The monkeys are an omnivorous species that lives in the southwest Amazon Basin across Peru, Brazil and Bolivia. They are not considered an endangered species, according to the Smithsonian, and typically live 10-to-20 years.
Contributing: Natalie Neysa Alund, USA TODAY
Follow Jordan Mendoza on Twitter: @jordan_mendoza5.
This article originally appeared on USA TODAY: Missing emperor tamarin monkeys at Dallas Zoo follow vulture, leopard