Once again, two German scientists have artificially inseminated a Woodland Park Zoo elephant in hopes of producing a second offspring from Chai, now 28.

It’s the fourth time over the past two years that Chai, an Asian elephant, has undergone insemination. She became pregnant last year, but lost the pregnancy at an early stage, the zoo said.

The sperm sample used Tuesday night was collected from Rex, a 39-year-old bull elephant at African Lion Safari, in Cambridge, Ontario. He has sired three offspring.

“The sperm samples were of very good quality, and the timing was excellent, giving Chai a very good chance at conception,” said Bruce Upchurch, Woodland Park Zoo’s curator of elephants and behavioral management. “If Chai has conceived, her due date will be in early 2009.”

The procedure was led by scientists Thomas Hildebrandt and Frank Goeritz from the Institute for Zoo Biology and Wildlife Research of Berlin, Germany; the zoo’s general curator, Nancy Hawkes; and Upchurch.

Elephants have a 10-foot-long reproductive tract that makes artificial insemination technically challenging.

“We’ll be following Chai’s hormone levels closely,” Upchurch said, adding the German scientists could return in late summer to confirm a pregnancy by ultrasound.

Elephant keepers kept Chai and her now-6-year-old calf, Hansa, occupied during the process by doling out favorite treats, including buckets of fresh pineapple, cantaloupe, apples and carrots.

Hansa was born in 2000 after Chai was sent to the Dickerson Park Zoo in Missouri, where natural breeding resulted in a pregnancy. Hansa was the first elephant born at the 100-year-old Woodland Park Zoo, which has no male elephants.

Insemination allows the zoo to keep Chai at home and keeps her with Hansa, the zoo said.

Successful reproduction of captive elephants may be critical to the species’ long-term survival. The Asian elephant is an endangered species, largely because of habitat destruction.

An Asian elephant’s life expectancy is 50 to 60 years.