(CNN) -- Over 130 rare African parrots were seized near midnight Monday from a woman officials say was smuggling the valuable birds from the Democratic Republic of Congo to Uganda, a frequent jumping-off point for lucrative European and Asian markets.
The woman was carrying what Ugandan authorities described as a fake permit to transport more than 500 prized African grey parrots. She was stopped by Ugandan officials along that country's Congolese border, they said.
Ugandan wildlife officials later discovered that the birds had been fed alcohol-laced sugarcane to make them drowsy for the journey.
Most of the parrots were taken to the Uganda Wildlife Education Centre, where they were reported to be in critical condition. A few of the birds died.
Dr. Noel Arinpeireho, a veterinarian at the center, said the surviving birds would be placed in quarantine and subjected to a series of medical tests over the next month.
"After the quarantine we shall sit down and decide where to take them, but they are going back to the wild," Arinpeireho said.
The alleged smuggler was being questioned by police in Kampala.
Illegal trade in African grey parrots has increased in recent years, according to Belinda Atin, a spokeswoman for the center. Last year, over 500 were confiscated from smugglers in Congo, and five were taken from Libyan Embassy staffers in Uganda.
The parrots, many of which are sold in European and Asian black markets, are generally estimated to be worth between $300 and $700 each, Atin said.
"It's a lucrative business now ... so it's gaining momentum," Atin noted.
The Congolese government has a strict annual export quota of 5,000 African grey parrots, according to Caroline Behringer of the World Wildlife Fund. Europe and the United States have a complete ban on the import of such parrots raised in the wild.
The African grey parrot is listed as having "near threatened status" by the International Union for Conservation of Nature. If current trends continue, they will eventually become endangered, Behringer said.
Journalist Tom Walsh, CNN's Waffa Munayyer, and CNN's Alan Silverleib contributed to this report