PORTLAND, Oregon- The Oregon Zoo 's pregnant Asian elephant, Rose-Tu, has gone into early labor, according to zookeepers.

Wednesday night, Rose-Tu was showing telltale signs that the birth was coming.

Animal-care staff reported that the Asian elephant, now in her 22nd month of pregnancy, is showing signs of discomfort, an event that usually indicates active labor will begin within 24 hours, said zoo spokesman Hova Najarian.

Once active labor begins, it could still be another day or two before the baby arrives, according to elephant curator Bob Lee, who s spent much of the past few days monitoring Rose s progress. Active labor in Asian elephants usually lasts at least 12 - 36 hours.

Rose s blood-progesterone level dropped noticeably a few days ago, and we ve been watching her 24/7 since, Lee said. But these things happen according to their own schedule. Rose is still happily munching on hay and bamboo. We re not too concerned about how much time it takes as long as Rose and her baby are safe and healthy.

He added that there are many risks associated with elephant births, so they will continue to monitor Rose-Tu and the baby very closely.

When Rose-Tu gave birth to Samudra in 2008, her labor lasted about 36 hours. And after giving birth to Samudra, who had never experienced a birth before, became very confused and agitated, which can happen with first-time mothers, according to Dr. Mitch Finnegan, the zoo's senior veterinarian. He said that in that case, keepers quickly intervened.

That last birth easily took a year off my life, Finnegan said. I hope this one goes easier.

Rose-Tu's fans can track all her updates on the zoo's baby elephant blog.

Rose-Tu is was placed in isolation and under 24-hour watch earlier in the week. Zookeepers have been spending the night in cots near the huge elephant, watching and waiting.

Raw video: Rose Tu in 'maternity ward'

The elephant will remain safely indoors until after the calf is born.

The Oregon Zoo has fifty years of experience in birthing and raising Asian Elephants, and a very high success rate to go along with it. Smith said they're excited for a healthy finish after 20-plus months.

Zookeepers have also chosen some name options for the calf. Once it is born, the public will get a chance to weigh-in, too.

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