A crackdown on the sale of quasi-legal narcotics marked a milestone Friday, according to the Metropolitan Police Department, which claims the last two stores known to sell the drugs have now closed. Officials warned, however, that sales continue on the Internet and by dispatch order.

Tokyo police and the government's anti-narcotic officers searched two stores selling drugs in the Kabukicho district of Tokyo's Shinjuku Ward, police said Friday. They arrested three men on suspicion of selling drugs officially dubbed kiken (dangerous) but which are not technically illegal.

With the closure of these two establishments, the number of stores nationwide known to retail the substances has dropped to zero, the police said. There were 215 outlets known to sell kiken drugs as of the end of March 2014.

Among the three arrested was Hiroshi Takahashi, 42, who allegedly sold kiken drugs to a buyer at one of the two stores on May 1, the police said. The buyer was an anti-narcotics investigator from the Ministry of Health, Labor and Welfare's Kanto-Shinetsu Regional Bureau.

The ministry said it has tightened sales of such drugs after a series of traffic collisions involving drivers who had used the drugs.

Since December, the health ministry and governors nationwide asked Internet providers to block access to 235 websites suspected of selling kiken drugs, and as of Thursday, 189 sites were closed or had ceased to sell such drugs.

But the number of online and delivery sellers of the substances is increasing, the police said, adding that they are trying to strengthen controls on such sales.