McALLEN, Texas A U-S Senate leader says today's fly-over of the Texas-Mexico border helps him better understand the need for more security.

Senate Majority Leader Bill Frist joined U-S Senator Kay Bailey Hutchison in the Border Patrol-led tour of a 25-mile long stretch of the Rio Grande.

The Blackhawk helicopter flew low enough for those on board to see tracks from illegal immigrants who'd recently crossed the river to slip into Texas.

The lawmakers also saw recently apprehended immigrants and loads of marijuana in a lockup at a Customs site in Rio Grande City.

Frist says seeing the river, the footprints, and what he called the "humanity itself" of illegal immigration firsthand -- has left an impression.

Hutchison is sponsoring a bill to allow local law enforcement agencies to arrest illegal immigrants.