Two monkeys were taken from the Dallas Zoo on Monday, police said, the latest in a string of odd incidents at the attraction being investigated — including fences being cut and the suspicious death of an endangered vulture in the past few weeks.

No arrests have been made in any of the investigations, and police have not said whether the incidents are linked.

Dallas police said they believe someone cut an opening in an enclosure and took two emperor tamarin monkeys, small primates with long whiskers that look like a mustache.

The incident follows the Jan. 13 closure of the zoo and a daylong search when a clouded leopard named Nova went missing.

She was eventually found near her habitat, but police said a tool had been used to cut an opening in its fencing. A similar gash also was found in an enclosure of langur monkeys, though none got out.

On Jan. 21, an endangered vulture named Pin was found dead, and the zoo said the death did not appear to be natural. Zoo President and CEO Gregg Hudson said the vulture had “a wound.”

Ed Hansen, chief executive of the American Association of Zoo Keepers, said he could not recall a zoo facing similar incidents with such frequency.