PORTLAND -- Oregon Zoo officials say a rare black rhinoceros en route from Kansas City, Mo., to Portland has died.

The 8-year-old rhino, named Kipenzi, died Monday night at the Phoenix Zoo after 18 hours of attempts to stabilize her.

“We tried to do the best we could. We had a lot of people who put in a lot of effort throughout the day -- not just our staff but lots of people here in the (Phoenix) valley trying to help,” said Phoenix Zoo spokesman Jim Brewer.

The trouble began before Kipenzi reached Phoenix. Once she had been transferred to an elephant barn at the Arizona zoo, animal biologists gently pulled her from her crate and began providing fluids and medications.

Brewer said the zoo even administered Valium to Kipenzi at one point because she “was in such a stressed, aggravated state.”

Kipenzi was on the way to Portland to attempt and mate with Pete, a male rare black rhino here.

Bill LaMarche with the Oregon Zoo says Kipenzi and Pete were recommended for mating by the Association of Zoos and Aquariums, in accordance with its species survival plan.

“Our heart goes out to the people of Oregon and Kansas City. We did all we could,” Brewer said.

Oregon Zoo Deputy Director Mike Keele called it a devastating loss for accredited zoos across the nation, since black rhinos are among the world’s most endangered animals.

The Phoenix Zoo has ordered a necropsy on Kipenzi in coordination with Oregon’s zoo officials, according to both LaMarche and Brewer.

Results could take up to two or three weeks.