Philippine authorities are tracking down 10 Indonesians and two Pakistanis who allegedly are plotting a new wave of bombings in the southern part of the country. Armed Forces Chief of Staff General Narciso Abaya said they were verifying a report from Immigration Commissioner Andrea Domingo, who suspects the 12 men - called the 'dirty dozen' by the authorities - to be members of the Jemaah Islamiah extremist group implicated in last year's Bali blasts. North Sulawesi's police chief, Brigadier-General Jon Lalo, is helping the military track down the 12 men. He and his aides arrived in the southern city of Davao on Thursday for a five-day visit. General Lalo reportedly handed over photographs of suspected Jemaah Islamiah members who might be operating on Mindanao. Five Indonesians have been blamed for the recent bombings at Davao's international airport and wharf. Two others reportedly trained recruits of the Abu Sayyaf extremist group in making bombs. Last year, Fathur Rohman Al-Ghozi, an Indonesian serving time for a series of bomb blasts in Manila in 2001, confirmed that some of his countrymen were behind terror attacks in the Philippines. Another Indonesian, Agus Dwikarna, was caught with bomb components just as he was about to board a plane out of Manila last year. Last Thursday, he lost an appeal before a Manila court to overturn his 17-year sentence. Last Friday's seizure by the military of 24 sacks of ammonium nitrate - an ingredient in explosives - from a fishing vessel off Zamboanga pointed to more bomb attacks. Philippine Foreign Secretary Blas Ople has called for improved joint border patrols with Indonesia to stop extremists from sneaking through the country's southern back door. The authorities said part of the problem was that suspected terrorists could easily blend with the large Indonesian population in the south, said to number between 12,000 and 20,000. To address the problem, immigration officials and the Indonesian embassy have started documenting illegally staying Indonesians in the southern Philippines.