Customs officers on Wednesday said they arrested five men and two women in a series of anti-drugs operations this month involving "space oil" and an anaesthetic called etomidate, which is illegal to posses unless prescribed by a doctor.

Officers said their operations led to the seizure of space oil capsules and etomidate powder with a total estimated market value of around HK$17 million.

"The gaining popularity of space oil or etomidate, which is currently a part one poison abused by the young people, has aroused our enforcement attention," said acting assistant commissioner Wong Ho-yin.

"The success of our enforcement in November demonstrates the strong determination of Hong Kong Customs in detecting the crimes relating to illicit etomidate or space oil," he said.

Wong added that etomidate can cause tremors, dizziness, hallucinations and even brain damage.