A ban on "legal highs" in the Republic of Ireland has been extraordinarily effective in wiping out the industry, police have said.

The blanket ban, known as the Criminal Justice Psychoactive Substances Act, was introduced five years ago.

Before the law was passed, there were about 100 so-called "headshops" selling legal highs across the state, but that number has since been reduced to zero.

"The headshop industry is gone," Det Supt Tony Howard told the BBC.

He is a member of the Garda (Irish police) Drugs Unit, which has been responsible for enforcing the new legislation.

"We were worried because we saw a whole generation of young people starting to experiment with these new psychoactive substances, and they'd generally be people who wouldn't have otherwise engaged in the misuse of drugs," he said.

"They thought it was safe because of the perception that these were legal highs."

When the blanket ban took effect, it became illegal to advertise, sell, supply, import or export psychoactive substances in the Republic of Ireland.