From Sky News:
The South African Airways employees were detained after 5kg of the drug - worth about £250,000 - was discovered in a bag on a flight from Johannesburg.
Crew members were arrested after UK Border Agency officers made the discovery.
A spokesman for HM Revenue & Customs Heathrow said those in custody would be interviewed by HMRC investigation officers.
On January 21, a 15-member flight crew from the same airline was detained after cocaine and cannabis worth £310,000 was found in three bags.
The 10 women and five men questioned over that incident were released on unconditional bail, and were due to report back to HMRC investigators at Heathrow Police Station on March 23.
South African Airways were unavailable for comment.