The traffic safety agency said it was working with the Florida Highway Patrol in the inquiry into Mr. Brown’s fatal accident. The agency cautioned that the opening of an investigation did not mean it thought there was a defect in the vehicle being examined.

The federal traffic safety agency is nearing the release of a new set of guidelines and regulations regarding the testing of self-driving vehicles on public roads. They are expected to be released in July.

At a recent technology conference in Novi, Mich., the agency’s leader, Mark Rosekind, said self-driving cars should at least be twice as safe as human drivers to result in a significant reduction in roadway deaths. “We need to start with two times better,’’ Mr. Rosekind said. “We need to set a higher bar if we expect safety to actually be a benefit here.”

Karl Brauer, an analyst with the auto research firm Kelley Blue Book, said the accident served as a signal that the technology might not be as advanced and ready for the market as some proponents have suggested.

“This is a bit of a wake-up call,” Mr. Brauer said. “People who were maybe too aggressive in taking the position that we’re almost there, this technology is going to be in the market very soon, maybe need to reassess that.”

Tesla said in its news release that it had informed the traffic safety agency about the accident “immediately after it occurred.” But the company reported it publicly only on Thursday, after learning that the agency had begun to investigate.

Mr. Brown had spent 11 years in the Navy and then founded a technology consulting company, Nexu Innovations, according to a May obituary of Mr. Brown in The Greensburg Tribune Review in Westmoreland County, Pa., where he had formerly lived.