Islamabad, Pakistan ? The younger brother of Hambali, al-Qaida’s alleged top agent in Southeast Asia, was under surveillance weeks before his arrest, Pakistan’s interior minister said Tuesday.

Rusman Gunawan was arrested Saturday in the southern port city of Karachi with 16 Islamic students from Malaysia, Indonesia and Myanmar. He was being interrogated at an undisclosed location in Pakistan, Interior Minister Faisal Saleh Hayyat said.

The minister said the questioning already had yielded results. Based on Gunawan’s statements, Pakistani authorities picked up four more foreign Islamic students Monday, he said.

The arrests highlight an elaborate network of links between al-Qaida and Jemaah Islamiyah, the terror group allegedly headed by Hambali.

Three of the students arrested over the weekend are the sons of Jemaah Islamiyah suspects jailed in Malaysia, said Edmund Bon, a lawyer in Kuala Lumpur for two of the imprisoned men.

Another reportedly graduated from an Indonesian boarding school run by Abu Bakar Bashir, Jemaah Islamiyah’s alleged spiritual leader.

Hambali, 39, was Southeast Asia’s most wanted man until he was captured Aug. 11 in Thailand by Thai police and U.S. intelligence agents. The Indonesian, whose real name is Riduan Isamuddin, was later handed over to U.S. authorities, who took him to an undisclosed location.

Jemaah Islamiyah was allegedly involved in last October’s bombings on the Indonesian resort island of Bali, which killed 202 mainly Western tourists, and the August bombing of the Marriott hotel in Jakarta.

Pakistani intelligence officials believe Gunawan, 27, was running Jemaah Islamiyah’s branch in this Islamic nation.

“Hambali’s brother was under surveillance for weeks,” Hayyat told The Associated Press. “Perhaps he was not aware that he was being watched.

“We are interrogating Gunawan to determine if he had any plan to harm Western interests. I think he will remain in our custody for some time.”

Many Jemaah Islamiyah leaders, including Hambali, were allegedly trained at al-Qaida camps in Afghanistan and dozens of Indonesian Islamic students are believed to be in the region.

Indonesian authorities said Monday they had no charges pending against Gunawan and would not seek his extradition.