Smugglers in recent weeks have been abandoning large groups of Guatemalan and other Central American migrants in Arizona's harsh cactus-studded Sonoran Desert near the border with Mexico, alarming Border Patrol officials who say the trend is putting hundreds of children at risk.

Collectively, more than 1,400 migrants have been left by smugglers in the broiling desert — or in one case in a drenching thunderstorm — in remote areas by the border since Aug. 20. One group was as large as 275 people.

"We've seen large groups in the past, but never on this scale," Tucson-based Border Patrol Agent Daniel Hernandez said. "It's definitely a serious concern because their safety is being put in jeopardy."

Hernandez said the latest case involved 61 people rescued by agents last week from rising floodwaters caused by unusually heavy rains in an isolated area and "it could have been a much, much worse situation if the rain continued."

Unlike Texas, where people turn themselves in on the banks of the Rio Grande, the smugglers in in Arizona have been dumping groups of migrant families on a remote dirt road running along the southern limit of the Organ Pipe Cactus National Monument west of the Lukeville border crossing with Mexico. Summer temperatures there can soar close to 120 degrees (49 Celsius).

The migrants are sometimes provided with food and water, but not always, and they often require medical care for back and ankle injuries or lacerations.