WASHINGTON (Reuters) - The United States on Wednesday urged Venezuela to release an American citizen, Joshua Holt, on humanitarian grounds, saying he was being held on “questionable charges.”

State Department officials met with Holt’s mother, Laurie, on Tuesday in Washington, spokesman Mark Toner told a news briefing.

He said Laurie Holt was also meeting with members of the U.S. Congress and other U.S. government officials over concerns about her son’s health, without giving any details. Holt, in his mid-20s, has been held in a Venezuelan prison since June 30 on weapons charges.

“We obviously share her concern for her son, who is a U.S. citizen who has now been detained in Venezuela ... on questionable charges for some 300 days,” Toner said. “We again call on the Venezuelan government to immediately release Joshua Holt on humanitarian grounds.”

The State Department said it had last raised concerns with Venezuelan authorities about Holt’s health, conditions of his detention, and his treatment on April 24.