Hugh McQuaid File Photo

Connecticut Attorney General George Jepsen wants the nation’s biggest oil companies to crack down on their franchisees who sell illegal synthetic drugs at gas stations and convenience stores.

Jepsen and attorneys general from 43 other states and territories sent a letter Tuesday to the presidents, chairmen and CEOs of British Petroleum (BP), Chevron Corp., Citgo Petroleum Corp., Exxon Mobil Corp., Marathon Petroleum Corp., Phillips 66, Shell Oil Co., Sunoco and Valero Energy Corp.

In the letter, the attorneys general write they have “deep concerns over the problem of gas stations and convenience stores operating under the brand names of your companies and selling synthetic drugs that are illegal and extremely dangerous.”

Synthetic drugs are illegal, the letter says, but “initial confusion surrounding the legality” enabled drug dealers to convince places like “smoke shops,” gas stations and convenience stores they were legal to sell to customers.

Though law enforcement agencies have been combating the drugs’ increase in popularity, widespread access has caused use of the drugs to soar, according to the letter.

Over the past few years, the letter says, “dozens of owners, managers and employees of branded gas stations and convenience stores have been arrested for selling synthetic drugs.”

More than 130 instances have occurred in 29 states, including multiple cases in recent months, according to the letter.

Media reports cite numerous instances nationwide in which gas station owners or workers were caught selling synthetic marijuana, cocaine-laced bath salts and other synthetic drugs in recent years.

Several Connecticut gas stations have been the sites of illegal drug activity, though not all of the gas stations and convenience stores have been owned by the oil companies named in the letter.

In October, for instance, an employee of Ravi Mart in New London was arrested after police said he was found with 145 bags of synthetic marijuana, known as “K2,” and 459 grams of marijuana. In November 2013, A Plus Sunoco in Branford was busted by police as being the center of a drug-dealing operation; a store clerk was arrested.

The attorneys general worry that the oil companies’ well-known brands may give some people the mistaken impression that dangerous synthetic drugs sold on their retail premises are safe and legitimate, according to Jepsen.

“The increase in emergency room visits from the use of these synthetic drugs is alarming,” he said in a statement. “Given the significant danger that these drugs present to children and others, we urge these oil companies to help reduce the risk by prohibiting the sale of these drugs at their retail locations.”

Synthetic drug use has become increasingly popular in recent years, according to the letter. In 2010, more than 11,000 people went to emergency rooms after using synthetic marijuana, it says, citing U.S. Department of Health and Human Services data. That number jumped to 28,000 emergency room visits in 2011 and the numbers keep climbing, according to the attorneys general.

They are asking oil company leaders to prohibit franchisees from selling any synthetic drugs, ensure the prohibition is understood by communicating directly with all franchisees and employees, establish a point person in their corporate offices for franchisees if they have questions about synthetic drugs, revoke franchisee relationships with gas stations or convenience stores that sell any synthetic drug and report to police any franchisee selling synthetic drugs.