Ottawa, Oct 17 (IANS) Canada has become the second country after Uruguay to legalise possession and use of recreational cannabis.

The nationwide market for cannabis opened Wednesday at midnight amid lingering questions about the impact on health, the law and public safety, the BBC reported.

Shops in the province of Newfoundland, the most easterly time zone in Canada, opened as midnight struck for the first legal sales of cannabis in the country.

The Government of Canada was expected to announce the pardon of Canadians convicted of possession of marijuana on Wednesday that could ease their travelling to the US, Efe news reported. 

Prime Minister Justin Trudeau would pardon individuals convicted in the past for possession of up to 30 grams of marijuana.

It is estimated that hundreds of thousands of people could benefit from the measure.

Preparations including mailings to 15 million households were afoot -- detailing the new cannabis laws and public awareness campaigns.

However, there remain concerns, including about the readiness of the police to tackle drug impaired driving, the BBC said.

Canadian provinces and municipalities have been preparing for months for the end of cannabis prohibition. They are the ones responsible for setting out many of the details -- as to where recreational marijuana can be bought and consumed.

This has created a patchwork of legislation across the country as jurisdictions choose more or less restrictive frameworks for selling and using cannabis, the BBC said.

A number of analysts have predicted shortage of the recreational marijuana in the first year of legalisation as production and licensing would continue to be ramped up to meet the demand, with the marketplace still in its infancy.

For many Canadians, the criminal record of possessing marijuana for recreational use means they cannot travel to the US.

A conviction for possession of marijuana allows US Border Patrol agents to prevent Canadian residents from entering their country since Ottawa shares that database with Washington.

US Customs and Border Protection spokesperson Todd Owen though said the amnesty would not guarantee people with criminal records of possession of marijuana to enter the US territory in future.

The recreational use of marijuana is legal in nine US states, as well as in Washington DC.