The small bags found inside the van being driven by an immigrant who was killed by an ICE agent in Houston this month did not contain drugs, the Harris County district attorney’s office has confirmed, contrary to initial statements from the federal government.

The driver, Lorenzo Salgado Araujo, 52, was shot during a traffic stop in early July, one in a string of fatal encounters as the Trump administration continues its immigration crackdown.

F.B.I. officials obtained a warrant to search Mr. Salgado Araujo’s van after telling a federal judge that they believed that a “crystal-like” substance in plastic bags inside the vehicle might be methamphetamine. But family members of the victim repeatedly disputed that claim.

The district attorney’s office on Friday confirmed that the substance tested negative for narcotics and illicit drugs. The office has declined to comment further on the test results, citing an ongoing investigation.

The area’s congresswoman, Representative Sylvia Garcia, said in a statement on Friday that the substance was an “electrolyte powder to stay hydrated working outside in the hot Texas summer.”

Ruby Powers, a lawyer for Victor Hugo Salgado Araujo, who is the victim’s younger brother and was a passenger in the van, previously said in a statement that the substance was granulated salt. She said that Mr. Salgado Araujo, a construction worker, often mixed the salt with water as a means of staying hydrated, a common practice among outdoor workers.

In a statement on Friday, Ms. Powers said that the federal government’s claims about the contents of the bags had diverted “attention from what actually matters in this case.”

“Lorenzo was shot, and no lab report answers for that,” she said, adding that Mr. Salgado Araujo’s family expects to receive full test results on Monday, which will confirm what, exactly, the substance is.

The dispute over the bags came after the F.B.I.’s application for a search warrant — a document typically filed under seal — was submitted publicly. The F.BI.’s Houston field office did not immediately respond to a request for comment on Friday.

“The attempt to cast a shadow over Lorenzo Salgado’s name has failed,” Ms. Garcia, a Democrat, said in her statement.

Mr. Salgado Araujo, who was from Mexico and had lived in the United States for 35 years, was on his way to a construction job on the morning of July 7 with his brother and two other workers when federal immigration agents tried to stop his van.

Federal officials have accused Mr. Salgado Araujo of ramming into an Immigration and Customs Enforcement vehicle before an agent shot him in the abdomen.

The agents had been searching for a different person, the Department of Homeland Security has said. The passengers in the van have disputed the agency’s account.

Mr. Salgado Araujo’s death added to a growing list of encounters between immigration agents and people in vehicles amid the Trump administration’s mass deportation campaign. About 20 people have been shot at in their cars, some of them fatally.

Within a week of the shooting in Houston, a federal immigration agent shot and killed a man in a vehicle in Biddeford, Maine. In the hours after the shooting, details emerged to suggest that immigration agents may have been seeking a different person.

There are multiple investigations into the encounter between agents and Mr. Salgado Araujo, including by local agencies that have said federal officials were not cooperating with their Houston counterparts. His brother, Victor Salgado Araujo, remains in ICE custody, Ms. Powers said on Friday. In her statement, she repeated a call for his release “so that he can participate fully in the investigation.”

Mr. Salgado Araujo was a husband and father of three children who was close to obtaining legal residency at the time of his death, according to his family.