Dallas Zoo animals have escaped, gone missing, or died under suspicious circumstances. Here's a full timeline of the incidents now under criminal investigation.

• A pair of emperor tamarin monkeys at the Dallas Zoo was recovered after going missing on Monday.
• The zoo experienced a string of "unusual" or "suspicious" incidents with its animals this month.

Two emperor tamarin monkeys went missing at the Dallas Zoo before they were found on Tuesday inside an abandoned house in Lancaster, Texas.

The circumstances of their brief disappearance remain unknown, but a Dallas Zoo spokesperson previously told Insider that it was "clear the habitat had been intentionally compromised."

The case adds to a string of mysterious events that occurred in January at one of the oldest and largest zoos in Texas. All incidents are currently being investigated by the Dallas Police Department. It's unclear if they are related.

Here's a timeline of the recent events:

January 13: A "suspicious" tear in a clouded leopard's habitat

A clouded leopard named Nova was reported missing on the morning of January 13.

Dallas Zoo officials said Nova was nowhere to be found in her habitat, prompting an hours-long search. The leopard was found unharmed that evening in the zoo, not far from the enclosure.

Dallas Police Department authorities said that a "suspicious" tear had been discovered in Nova's enclosure and believed it to be a result of an "intentional act" using a cutting tool.

A criminal investigation was opened, according to Sgt. Warren Mitchell.

Additional cameras and on-site security patrols were added to the zoo's facility following the incident.

A day after Nova went missing, zoo staff also discovered a similar cut in the langur monkeys' enclosure. Police are saying that the tear was also likely intentional.

January 21: An endangered vulture dies under "unusual" circumstances

About a week after Nova escaped her enclosure, the Dallas Zoo said in a statement that one of its endangered vultures, named Pin, was found dead in his habitat.

Little details were shared about the 35-year-old vulture's sudden death.

"The circumstances of the death are unusual, and the death does not appear to be from natural causes," zoo staff wrote on Twitter.

The Dallas Police Department is investigating the matter.

January 30: Two emperor tamarin monkeys believed to be "intentionally taken"

A pair of emperor tamarin monkeys were discovered missing on the morning of January 30, according to the Dallas Zoo.

"It was clear the habitat had been intentionally compromised," zoo staff wrote on Twitter. "Emperor tamarin monkeys would likely stay close to home — the Zoo searched near their habitat and across Zoo grounds, and did not locate them. Based on the Dallas Police Department's initial assessment, they have reason to believe the tamarins were taken."

The Dallas Police Department said its preliminary investigation found an "intentional cut" to the monkeys' habitat.

"Two monkeys are missing, and it is believed the animals were intentionally taken from the enclosure," DPD said in a statement.

The duo was found on Tuesday evening after the DPD received a tip that the monkeys may be located at an empty home in Lancaster, Texas.

"Our veterinary and animal care teams have said, beyond losing a bit of weight, they show no signs of injury and both started eating and drinking almost immediately once the team completed health exams on Tuesday night," the Dallas Zoo said in a statement released Wednesday.

Police said an investigation into the incident is ongoing, and it remains unclear if it is related to the recent string of mysterious cases at the zoo.

The zoo has also offered a $25,000 reward for more information that may lead to an arrest and indictment.