More immigrants have been drowning in the Rio Grande over the last six months.

Authorities say that's because immigrants are choosing more dangerous crossings into South Texas to avoid detection. Many of the bodies have been found in the weed-choked irrigation canals that feed into the Rio Grande.

The Border Patrol has responded by expanding its search-and-rescue teams to monitor the area.

The Rio Grande Valley has seen at least 16 drownings since October, and nearly a third of them were in the canals. The tally is only five short of the number of deaths reported from October 2013 to September.

Mission Fire Chief Rene Lopez Jr. says his rescue team would normally recover one body a month from canals. In January and February it was about one a week.