Police in the Philippines say they've arrested four people who allegedly hacked into AT&T's phone systems as part of a plan to funnel money to a Saudi-based terror group.

The Philippine Criminal Investigation and Detection Group said it worked with the U.S. Federal Bureau of Investigation to arrest the suspects late Thursday. The hackers, according to investigators, worked for a group that helped finance a deadly 2008 terrorist attack in Mumbai, India.

They say that the hacking cost AT&T around $2 million, though AT&T couldn't immediately comment Saturday.

The arrests stemmed from a complaint filed by AT&T and the FBI.

AT&T Inc., based in Dallas, said last Tuesday that hackers unsuccessfully attempted to link mobile numbers with online customer accounts. It's unclear if that incident is linked to the arrests.