Wellington, March 6 (DPA) The main ingredient in fake Viagra seized by New Zealand customs officers was guano - bat and bird droppings - a newspaper reported Saturday.

Other medicines intercepted contained whole insects, dust mites, hair and charcoal, Dallas Mildenhall, principal scientist at the state-owned GNS Science research organisation, told The Press, of Christchurch.

The paper said a Viagra pill could cost about 25 New Zealand dollars ($17) in New Zealand, but they could be ordered on the internet for just $1 to $2.

'It's a big public safety risk,' Clare Strachan, a researcher at Otago University, said.

She said a study of intercepted imported medicines found many were mouldy and contained more or less than the amount of medication stated on the packet, while some contained a completely different drug than the one ordered.