By Jim Forsyth

SAN ANTONIO (Reuters) - A man campaigning near a polling place in Texas on the state's primary election day on Tuesday was shot and wounded by gunfire from a passing vehicle, officials said.

"We are not sure why he was shot, just that a vehicle drove by and shot at him," Hidalgo County Elections Administrator Yvonne Ramon said.

She said the victim, Jose Sanchez, 55, was standing across the street from a polling place in San Juan in South Texas, holding a campaign sign. He was hospitalized for treatment after the shooting.

"He was there doing a job and supporting a particular candidate when this happened," Ramon said, adding that she did not know which candidate Sanchez was supporting.

Texans on Tuesday headed to the polls to cast ballots in Republican and Democratic primary elections, including local races, a U.S. Senate race and the presidential contest.

(Editing by Corrie MacLaggan and Cynthia Johnston)