Manila, March 16 -- The Bureau of Immigration (BI) on Sunday said it is ramping up its internal investigation following the re-arrest of South Korean fugitive Na Ikhyeon, who escaped under suspicious circumstances.

BI Commissioner Joel Viado, at the same time, warned that more employees are facing suspension for possible involvement or negligence.

Na, wanted in South Korea for fraud and other charges, was initially arrested in the Philippines but managed to escape while in BI custody on March 4. He was recaptured on March 9.

"This incident exposed deep-rooted problems within the system. This is not a simple mistake. There's collusion here," Viado said in Filipino, as quoted in a news release.

"We are identifying more personnel who may...