SAN DIEGO (CNS) - Three small brush fires broke out in a remote area along the U.S./Mexico border Friday and firefighters had to be flown in to fight it, authorities said.

The fires -- the largest of which was two acres -- were reported at Doghouse Junction and Otay Truck Trail about 5:40 a.m., according to Cal Fire spokeswoman Roxanne Provaznik.

Because of the remote location, fire crews needed to flown in by helicopter, she said.

The cause was under investigation.