MANILA (Reuters) - Philippine immigration authorities freed four East Timor delegates after holding them for 12 hours at Manila airport in a security clampdown ahead of the ASEAN and East Asia Summit next week. The four East Timorese were allowed into the Philippines but authorities kept their passports until a formal order is issued clearing their entry, said Rhoda Viajar, media relations of the ASEAN Civil Society Conference/ASEAN People s Forum. Immigration authorities said the four were held upon arrival on Saturday morning because they could not explain the purpose of their travel and were  not able to establish financial capacity for the visit .  The civil society conference organizers understand the more stringent security measures being implemented due to the upcoming ASEAN summit,  Viajar said. She said they  remain concerned about the possibility of similar incidents upon the arrival of many more participants from other countries . Since 2005, ASEAN leaders have held a dialogue with the region s top civil society groups to listen to development concerns and address critical issues such as poverty, health and education. Philippines security forces are deploying nearly 60,000 army and police personnel during the Nov. 10-14 ASEAN and East Asia Summit to ensure the safety of 19 world leaders and thousands of delegates from 10 Southeast Asian nations and 10 other dialogue partners, including U.S. President Donald Trump.  We have not monitored any real and direct threat in the national capital region, but we are not complacent,  national police chief Ronald dela Rosa told reporters after reviewing security preparations on Sunday.  There could be threats but we are ready and we are up to the challenge.  Police will deploy 400 mobile patrol cars, 200 motorcyles, 22 armored vehicles and 100 bomb-sniffing dogs to ensure the security and safety of leaders, officials and delegates to the biggest regional summit in Manila this year.     Some areas will be completely locked down, such as where heads of state and governments will hold meetings. Main roads running from the former U.S. air force base about 90 kms north of Manila to the venues will be partly closed. Interior Undersecretary Catalino Cuy said there was no plan to jam mobile phone signals to prevent potential crude bomb attacks because this would cause inconvenience for state officials and security personnel. 