Threats in the form of a suspicious powder have been received by several of the drivers accused of using a west-metro interstate for a racetrack recently in exotic sports cars at more than 100 miles per hour, a defense attorney said Monday.

“Several of the individuals have received anonymous packets in the mail containing white powder,” said Marsh Halberg, who is representing at least four of the 12 defendants charged with reckless driving in connection with the high-speed cruise on April 23 along westbound Interstate 394 that continued after the route changes to Hwy. 12.

“There is a genuine concern for the safety of the individuals at this time,” Halberg said. He added that there have been no ill-effects from the contents of the packets.

Halberg said the packets have been turned over to the FBI, which “has been very responsive” as it investigates the items.

An FBI spokesman declined to confirm or deny that it’s looking into the matter, a standard response unless the agency is seeking public assistance in an investigation.

There’s been no determination yet on the makeup of the white powder, Halberg said. “I don’t want to speculate on why someone would send the envelopes,” he added.

Soon after the terror attacks on Sept. 11, 2001, letters containing anthrax spores were mailed to several news media offices and two U.S. senators, killing five people and infecting many others.

Since then, federal agencies have investigated and charged numerous people nationwide with biological-weapon hoaxes and threats. Many of those hoaxes involve what was presented as anthrax, a white, powdery substance.

Halberg would not identify the clients who have received the white powder. He said one envelope went to a business and the rest to residences.

The 12 cars that were stopped and several others that were not caught left Morrie’s Luxury Auto sales near Louisiana Avenue late that Saturday afternoon and sped west on I-394.

The 12 drivers stopped, some of whom belong to a Twin Cities sports car club, were pulled over by the State Patrol in two groups and cited for reckless driving.

The vehicles “were changing lanes and passing other motorists at high speeds,” the patrol said in a statement.

At least one woman attending that pre-cruise gathering as a model went along as a passenger in one vehicle and shared her impressions of the thrill ride in an Instagram video titled “Pulled over the whole cruise,” which showed patrol cars and some of the luxury cars stopped in a clump.

“Yesterday’s cruise with MNE & S [MN Exotics and Supercars] was interesting,” she wrote on Instagram. “It was a good experience though.”

Two of the drivers tentatively have a June 6 court date to answer to the misdemeanor charge, and the rest are scheduled to appear a week later.

“I don’t think there was any plan to go off speeding” when they left their gathering spot,” Hallberg said.

The attorney declined to say more, he said, wanting to see what evidence the patrol has gathered, including video from the traffic cameras along the route.