OTTAWA - Canadian military police have started using drug dogs to search troops' bags at Kandahar Air Field after being tipped about soldiers suspected of using heroin, hash and pot, say newly released documents.

Although there were no drug seizures reported, a briefing note says illegal drugs are readily available in Afghanistan and present a "temptation for Canadian troops in the form of personal use and in the form of importation for the purpose of trafficking."

The documents, obtained by The Canadian Press under the Access to Information Act, indicate there were at least five targeted and random searches of soldiers' belongings in June and July at Kandahar Air Field.

The Canadian Forces National Investigation Service, an independent military police unit, used dogs trained to sniff out drugs to search about 90 soldiers and more than 100 barrack boxes.

Military police took the names of soldiers in a convoy that was searched following a tip in July.

The briefing note says that search didn't produce enough evidence to justify charges, but military police were to check their records "for any other indication of illicit drug use/trafficking" among those in the convoy.

It's unclear why military police did the background checks because an e-mail outlining the incident was partly censored.

Defence Department spokeswoman Capt. Julie Roberge said she wouldn't comment on specific searches.

She said the military uses the dogs if it has a "reasonable doubt" there may be drugs at Kandahar Air Field or at one of the forward operating bases.

"As soon as there's a doubt ... of course there's going to be a follow up," Roberge said.

She said the dogs are a "NATO asset" shared among coalition forces. The Canadian military is field-testing its own drug-sniffing dogs in Canada with the intent of eventually using them in Afghanistan, she added.

Liberal defence critic Denis Coderre, who travelled to Afghanistan last month on an unofficial fact-finding trip, said he saw no evidence of drugs nor did he witness any dog searches.

The briefing note raised questions about whether the searches violated soldiers' Charter rights, particularly their expectation of privacy and the right to be secure against unreasonable searches.

But it concludes that targeted and random searches of convoys are an "effective and efficient method" of deterring troops from using or trafficking drugs without negatively affecting operations.

Word of the Kandahar searches follows charges laid last week against an Ottawa-based soldier for allegedly trafficking pot and hashish after an 11-month undercover sting operation by the military police unit.

Master Cpl. Steven Pearson was charged with five counts related to the alleged trafficking and possession of marijuana and hashish dating back to January 2006.

There have been several other high-profile incidents in recent years of alleged drug trafficking within the military.

Four crew members of HMCS Saskatoon were charged this year after a military police unit launched an undercover sting operation targeting the small coastal patrol ship in early 2006.

A court martial for one officer charged with trafficking cocaine and disgraceful behaviour under the National Defence Act has been adjourned until next year.

Two other crew members pleaded guilty and were given suspended sentences and fines, while the third was cleared of one charge and had a second one stayed.

Last year, five soldiers were charged at Canadian Forces Base Gagetown, N.B., under the National Defence Act with trafficking in cocaine, ecstasy and marijuana.