SACRAMENTO, Calif. -- Relatives of a Lodi father and son held on terror-related charges were summoned to testify before a federal grand jury Thursday.

The father and son (both pictured, below, in a court drawing) -- Hamid Hayat, 22, and Umer Hayat, 47 -- have only been charged with lying to investigators, but they are suspected of having ties to al-Qaida.

Walking out of federal court with his attorney Thursday, the Hayats' relative -- Kaashif Altaf (pictured, left) -- said he could not discuss why he was called before a federal grand jury.

Altaf was subpoenaed to testify in an ongoing case that the government claims puts his uncle and cousin at the center of a terrorism cell based in Lodi.

The younger Hayat is accused of admitting, then denying he attended an al-Qaida-style training camp in Pakistan. His father allegedly lied about helping fund his son's training.

Altaf was one of at least three family members called to testify Thursday. According to two published reports, the government issued subpoenas only after those same family members refused to submit to FBI interviews.

Family members have told KCRA 3 that Hamid Hayat did not attend a terrorist camp and that he has no interest in political matters.

Although no terrorism-related charges have been filed against the Hayats, government prosecutors have continued to say the case in an ongoing investigation and more charges could still be filed.

Lead prosecutor Steve Lapham declined to comment about the case, saying: "No comment, sorry."