DENVER -- The Denver Zoo will be closed Thursday for a memorial in honor of a zookeeper who was attacked and killed by a jaguar on Saturday.

The zoo said it has planned a private memorial for 28-year-old Ashlee Pfaff on zoo grounds Thursday. Pfaff was attacked by a jaguar when she opened a door from a service area into his enclosure when the cat was still inside.

The zoo will reopen Friday at 10 a.m.

Zoo officials said they do not know why Pfaff made direct contact with the jaguar since the zoo policy forbids keepers and big cats from being in an enclosure together.

The zoo, Denver police and the U.S. Department of Agriculture launched investigations into the incidents.

Zoo officials said there was no evidence of faulty locks, gates or doors to the jaguar's enclosure. Pfaff was an experienced zookeeper and the jaguar had no history of unusual behavior, zoo officials said.

The feline cage remains closed to the public as the investigation continues.